Hi, more electricity heading your way. As voted by you guys, here is Kawaguchi making his debut in Dr Yukimura!

Kawaguchi's POV:

It was a slow school day today. I had my hands in my pockets while I walked back to class. E Class was mostly empty as usual, since everyone hung out with their friends and stuff. The 2 of the Big 3 Loners were here, unsurprisingly.

Kouji sat at the back, sleeping lunch away, while Takanori was playing on his phone. Ikesugi's the odd one out since he's gone to play basketball or something. All three of these guys are pretty solitary in their own right.

Kouji doesn't want any friends or communication. He just ignores everyone around him. Takanori can talk... but he's a complete socially awkward nutcase. Ikesugi doesn't hold back regarding his opinions. Pretty sure he's said some snarky remarks to the girls which made them hate him.

At one of the tables, I saw Yukimura and Nora sitting together with some books open.

"Hey you guys." I said.

"Huh? Kawaguchi, sup." Yukimura fist-bumped me.

"What are you two doing out here? Wouldn't the library be better to study?"

"Mikitaka and his crew raided the place so me and Nora left to study here." Yukimura said.

"Unfortunately..." Nora mumbled afterwards. I couldn't hear what he said after.

I pulled up a seat and sat down. "So, what you studying?"

"Physics."

"Seriously? Dude, your score on science sucked."

"That's why I'm revising, idiot."

At least he's trying to improve. I smiled and laughed.

"Yeah, yeah. Want me to help? I got a good score."

"What the hell did you even get?"

I cast my mind back to the mock exam. I thought hard and long but...

"I completely forgot! It was more than yours, though."

"You little—"

Yukimura balled up his fist with his pen and nearly hit me with it. However, Nora cut in.

"He got 10."

"What? That's only 3 more than me! Bwa ha ha ha!" Yukimura put his pen down.

Thanks for the save, man.

"Since my score sucked too, I want in."

"I don't think I can teach two people..." Nora said.

"Have some know confidence. You're smarter than both of us, so it'll rub on us eventually."

Nora was an academic beast. Second best to Sakigamiya. Though, Sakigamiya makes it look easy. She's never seen revising, but instead talking to others. Nora on the other hand is always reading books and doing homework.

Then there was me and Yukimura. We were pretty alike. We both cram the day before the exam. We both don't really care and just take it easy in lesson. Though, I seem to remember more than he does.

"Why're are you hanging with us anyways? Don't you and Ishima usually play Vanguard?"

"Aki-san is talking to his sister about something."

"Ho? I still find it funny he got dumped in E Class while his sister is in A Class. She has a cute face, won't lie."

"Let's not talk about girls and focus on our studies..." Nora said.

"Yeah, yeah, whatever." Yukimura growled. "Don't just stand there. Take a seat if you seriously want to learn."

"Was just about to." I sat down. "Which topic?"

"Electricity. I did some practical yesterday but still need to sharpen my skills." Yukimura said.

"We're going over the basics of circuits." Nora said.

"Alright, sounds good to me."

Circuits... electricity, then. Well, my dad has a degree in science, so this shouldn't be hard for me, right? Though, his degree's in biology... specifically the human body... that's a far cry from electricity... if it was chemistry, then at least I'd have electrolysis!

"Let's look over series circuits, the most simple one. The practical you did yesterday involved a series circuit because the electrical components are connected one after another in a single loop."

Nora began drawing out a circuit on his notebook. Yeah, I've definitely seen that before. In middle school, I think? Though, I didn't pay much attention back then... I wasted my time in class messing around with everyone else.

It was absolute chaos in that classroom.

"In a circuit, there are rules. One of these is an electron will pass through each component in a circuit. That means if one bulb breaks, the rest of them also go out. This is because the current can't flow around the circuit since it can't get past that component."

"Oh, so it's like Vanguard. You guard with your units, and if your opponent drive checks a trigger, the shield breaks and you get dealt a damage. Since that damage was the 6th one, you die, like all the bulbs."

"Umm... well, if you put it that way... I suppose it kind of works like that."

"What the fuck..." Yukimura muttered, giving me a disgusted stare. "How much do you and Mitsuba love Vanguard? Jeez."

"Vanguard's like the only thing I'll ever get in this world." I laughed.

Vanguard let me escape from my regrets in middle school.

"Anyways. All the electrons flowing through this series circuit form a single current. You can use an ammeter to measure the current. It doesn't matter where you place it, since the recording will be the same."

"So if you place an ammeter on any rear-guard circle, the current will be the same?"

"Y-Yes...?"

I think I'm confusing him with these Vanguard comparisons.

"Kawaguchi, just shut up!" Yukimura said.

"Right, right, sorry." I stuck out my tongue and laid my head on the table. "Please, continue."

"Um... so for potential difference... since the current transfers energy from the power supply to the component in the circuit, and we know that energy has to be conserved, all the source energy must be shared between the components. Since potential difference measures the change in energy, the voltage supplied is equal to all the total of the potential differences across all other components."

"So you add the potential difference of each component together to find the voltage supply?" I asked.

"Yes."

"Sick."

"Now, if resistors are connected in series, the current has to flow through both of them, increasing the resistance. To find the total resistance, you add the resistances together."

"This is easy." Yukimura said.

"You jinxed yourself." I said.

"Well, Kawaguchi-san has a point. This is just a basic series circuit. The parallel circuit is more complex."

"It's just a circuit, isn't it?"

"It is but... you'll see when we get there. As a quick recap for series circuits: current is the same through each component, the total potential difference of the power supply is shared between components, and the total resistance of the circuit is the sum of the individual resistors."

Nora becomes really confident when he starts explaining this sort of stuff. He'd make for a good tutor. Maybe not a teacher. He's too weak-willed for that.

Plus, some classes are plain unruly... like E Class. If he had to teach that class, there'd be no chance he'd have control.

He flicked to the next page of his revision guide and began skimming the page. Yukimura scratched his head as he took notes down into his scruffy book.

I mean, in my old school, a student stabbed a teacher. He got expelled, like a few others. That class was nicknamed "the Classroom of Chaos". All the teachers who taught that class ended up quitting after a month.

"In parallel circuits, electrical components are connected alongside one another forming extra loops. The rules for this circuit are slightly different."

I was one of the students in that class.

Guess it's why I'm not surprised that I ended up in E Class. I should've saw it coming.

"An electrons will not pass through every component on its way around the circuit. If one of the bulbs break, then the current will still be able to flow around the circuit through the other loop. If one bulb goes out, the rest will stay on."

Considering what I did, there was no way I'd be allowed to be in any other class than E.

I'm surprised they even invited me in the first place.

"Huh, that's more useful than a series circuit. If one of those bulbs goes out, the entire circuit dies. This one at least can continue going." Yukimura said.

"Yep. Parallel circuits are more commonly used in real life for that reason." Nora said. "Since there are different Loop,S the current will split as it leaves the cell and pass through one or other of the loops. An ammeter placed in the different parts of the circuit will show how the current splits."

"So if the total current is 5, when it splits through the different loops, it'd be 3 and 2 or something like that?"

"Yes! You grasp things really quickly, Yukimura-kun!"

"I'm pretty sure it's just because it's easy..."

At least someone's having success with this revision.

"Now onto potential difference in parallel. As energy has to be conserved, the energy transferred around the circuit by the electrons is the same whichever path the electrons follow. Since potential difference is used to measure changes in energy, the potential difference supplied is equal to the potential differences across each parallel components."

Yukimura scratched his head.

"Um... was that too complicated of an explanation?" Nora said. "S-sorry... I just like going in detail..."

"So, in other words... the voltage around a parallel circuit is the same regardless of the loop it goes through...?" Yukimura said.

"Yeah, that sounds correct." I decided to interject. "I mean, voltage doesn't work like a current. If a current goes round the circuit. Voltage is the thing that pushes the current around. It'd be the same push everywhere."

"It looks like you did understand it... phew." Nora said, patting his chest.

"Yukimura-san looks like a dummy, but he's surprisingly adept at this, isn't he?"

"He did put in the effort beforehand... to try and learn electricity earnestly. I'm just trying to... clear it up for him. You're not doing bad either, Kawaguchi-san."

"Heh, thanks. You just explain things well."

It made me wonder. What was I good at?

"If resistors are connected in parallel so that the current will flow through either one or the other, but not both, then the overall resistance is reduced."

"Seriously? I thought it'd increase..." Yukimura said.

"Well, in a parallel circuit, there are different loops the current can take. If the resistors are placed in parallel, the current can follow multiple paths, reducing the resistor's effectiveness. You're not passing through two resistors after all, like in a series circuit."

"Oh, I see. Okay, guess that makes more sense. It's because you're going through a single resistor compared to two and that there are multiple routes for the current to take."

I've always excelled at games. In the end, an exam is just a game, isn't it?

There are winners, there are losers. You can even draw with someone else. There are rules, and there are different methods of attacking and defending. You build your deck - your head - before the battle.

"So let's recap. In parallel circuits: the total current supplied is split between the components on different loops. Potential difference is the same across each loop. The total resistance of the circuit is reduced as the current can follow multiple paths."

By changing my perspective slightly, it makes the exams feel doable.

"The next part is a practical exploring the series and parallel circuits... Um, if you want, I can just explain it to you. I don't feel like going to Ike-sensei's lab when lunch is going to end soon..."

"Yeah, explaining is fine. Make sure to draw some beautiful diagrams!" I said.

"O-Okay. So, this practical has you investigate resistor networks. You have to set up a series circuit like this. It only needs a resistor, an ammeter and a voltmeter in parallel. You record the voltmeter and ammeter readings and use them to calculate the resistance using the equation R = V/I. It's resistance equals voltage divided by current."

Nora drew a diagram of the circuit and then wrote down:

Resistor: R1
Voltage: 4.00
Current: 0.40
Resistance: 10

"Then you repeat this, but this time, you change the resistor for another one to find a resistance of a second resistor."

He then wrote down more readings:

Resistor: R2
Voltage: 4.00
Current: 0.40
Resistance: 10

"Then you'd do it again, but this time have two resistors in series. It would look like this."

Once again, he drew a diagram and wrote some readings down:

Resistor: In series
Voltage: 4.00
Current: 0.20
Resistance: 20

"Notice that by having two resistors, you increase the resistance? It also equals the two resistor readings we put earlier."

That was, admittedly, pretty cool.

"So I'm guessing the next one is parallel?"

"Yep. It'd look like this and the readings would be like this..."

Resistor: In parallel
Voltage: 4.00
Current: 0.80
Resistance: 5

"So in this case, the resistance actually halved from it's original. Analysing this data tells us that in series circuits, the resistance of the network is equal to the sum of the two individual resistances, and in parallel, the resistance of the network is less than either of the two individual resistances."

I yawned. Revising was really not my thing...

I appreciate the explanation and all, but I'm bored to death about electricity.

"In conclusion, by placing the resistors in series, it causes the resistance to be double that of a single resistor, because there is only one path for the electrons to follow. The supply must drive current through one resistor and then the other."

I reached into my blazer pocket and drank some bottled green tea. I really shouldn't have bought this since I'm strapped for points, but I love this drink.

"Placing the resistors in parallel causes the resistance to be half that of a single resistor. The outcomes of this experiment would be the same if you used a filament lamp, since lamps act as resistors too."

I pulled out my phone and went onto the school app to go to my account. Checking my balance, I cringed at the total of points I had left: 2,570 private points. I was really screwed.

At least I lived in the dormitories... there'd be no way I could pay rent with those numbers.

"What's with the sulky face?" Yukimura laughed at me. "Is this too hard for you, Kawaguchi?"

"No, there's something even worse..."

"What?"

I showed Yukimura and Nora my measly balance.

"How the hell did you spend more than me? I thought going down to 8000 was cutting it..."

"You two are so reckless with your spendings..." Nora sighed, shaking his head.

"How many points do you have?" I asked.

"Around 70,000..."

"What the hell?!" Me and Yukimura exclaimed together.

"You barely touched your points!" I said.

"I would have more, but I had to pay some points for the house..."

"Yeah, must be nice living in an actual home..." Yukimura muttered. "I hate the dorms. They suck."

"Could be worse." I shrugged.

"Now let's look at energy and power in electric circuits." Nora said. "As electrons flow through wires, they collide with ions in the wire which causes the ions to vibrate more. This increased vibration of the ions increases the temperature of the wire. Energy has been transferred from the chemical energy store of the battery into the internal energy store of the wire."

So, basically, when collisions happen, vibrations occur, and the wire gets hotter.

"The amount of energy transferred each second, power, between the energy stored can be calculated using this equation."

Nora wrote onto his notebook: Power = Current x Potential Difference. Or in it's short hand form, P = I x V.

"Power is measured in watts. Current is in amps and potential difference is in volts. One watt is equal to one joule per second, J/s. Power dissipated in a resistance can also be written as Power = Current^2 x Resistance."

So P = I^2 x R in the short hand form. I hate that there's so much math in physics.

"Same units of measurements, but resistance is measured in ohms. Here's an example. How much energy is transferred each second by a current of 2 amps driven by a potential difference of 230 volts?"

"If you have current and voltage... you use the power equation P = I x V." I said.

"Oh, multiply them together. Uhh..." Yukimura came to the right conclusion, but couldn't even double 230.

"460 watts." I said for him.

"Yep! How about this one. What power is dissipated by a current of 3 amps through a 10 ohm resistor?"

"Oh, the squared equation. 3 squared is 9... 9 multiplied by 10 is 90. So 90 watts."

"Correct! Kawaguchi-san, you're on fire today!"

Yukimura rubbed his temples and wrote some scribbles in his notebook. He looked really agitated.

"I hate the math part of this. Can we move onto something else?"

"S-sure... Um, this is the last part of this section. Efficient transmission of power."

"Question, will there be math?" I raised my hand. Yukimura hit me in the ribs and I laughed.

The guy has a strong punch, even more so when he's frustrated. For someone who got it easily at the start, it's just been downhill for him since.

"No... but we'll have a look at the second power equation."

"Alright, sure. Hit me with the facts."

Though, I felt Yukimura's suffering. I was bored out of my mind at this point. I don't think I understood what he was saying at all.

"Energy can be transferred by an electrical current. Any electrical appliance needs to be given enough energy every second. Like a kettle to boil water. Electrical power can be delivered as a low current with a high voltage, or a high current with a low voltage."

Alright, let's try to focus. I've heard of this before. The bit about power being delivered as a low current with high voltage or vice versa.

"This is why we have the equation power = current^2 x resistance. The equation shows that a high current will have a much higher heating effect on the transmission wires than a low current."

It's probably because a higher current means more collisions, which results in more vibrations, which results in a higher temperature.

"For this reason, transmitting energy at a high voltage with low current will keep wires cooler and waste less energy."

Makes sense. High voltage will push the current around more, and keeping the current low means there's less collisions, since there are less electrons in the wire.

"Reducing the resistance of the wires will also reduce unwanted energy transfer, but reducing the current will have a much more significant effect."

Since resistance slows down current, it makes sense that reducing it would also reduce unwanted energy transfer, since it reduces the collisions. Though, a low current would just cut the problem of excessive collisions completely.

"And that's the end of the section. Good job you two... especially Yukimura-kun. You worked really hard today."

Ah man, if only Nora was a girl. He's got the cutesy feminine voice, but he looks like a boy. If a girl told me that, I'd be way happier.

Yukimura sighed and rubbed the back of his neck.

"Thanks Nora. Though, I don't feel confident." Yukimura said, with honesty in his voice. "I'm not cut out for science at all! I struggled to follow you at the end."

"D-don't be so hard on yourself... you really did try your hardest, right?"

"Of course I did... but I still messed up in the end. Studying's hopeless for me. Ugh, I'm so not scoring 80% on the midterms..."

I flinched.

"Oh crap... we have midterms don't we..."

"Unfortunately. If I get 80% or more, I get to go to Sakigamiya-san's apartment. Please God, let me score well on this exam!"

No wonder he was actually studying for once...

"If you really do want to... go to Sakigamiya-san's apartment... you should believe in yourself more... don't forget about what Ibarada-senpai told you... you're a natural for science... and I think so too. Even if you believe your terrible at this subject... you'd be surprised at how much you remember. So don't give up... because if you give up now... you'll regret it when we do the midterms...!"

Nora gave a heart warming speech. If he was a girl, I'm 100% sure Yukimura would go wild and try his best to study. Nora, you were cursed with the wrong gender.

Yukimura squeezed his fists and gritted his teeth.

"Y'know, he's right. If you give up now and never try to take a step forward... you'd only be hurting yourself. Even if you're not good at it now, if you continue to study over time, it'll grow in small steps. That's how you became good at sports. Because you didn't give up. You weren't gifted with a six pack and muscles. You worked hard for it. That's proof enough that you can achieve your goals."

Yukimura let out a deep breath and looked up with conviction.

"You're right, Nora. If I didn't study or try, I'd regret it. You're right too, Kawaguchi. I've had to do hard work before. I can't give up at this crossroad. I'm fighting to run towards the correct path. The one where me and Sakigamiya-san are a couple!"

He's got the vigour to keep going.

And that's the most important thing.

To never give up.

That's the most important lesson my parents taught me.

Even though I disappointed them by—

I said I'd never give up to grow up into a mature person to confront my past.

Yet my body feels paralysed with a pulsing pain.

An undeniable fear that I never want to return to that place.

To never look at the scenery engulfed in a light stronger than the sun.