(Quick A/N - I realised I completely messed up somewhere along the line. (Y/N) is a third year. I've started backtracking and fixing bits and pieces, so let's pretend I was actually good at basic math and forget I did a big fat oopsie xD)
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"Did you hear that news report last night?" I heard someone speak up as I walked down the hallway. I forced myself to go back to school after Dabi stayed with me for three unnecessary days. It was nice; just talking and lazing about, stuffing our faces, even after my parents had returned. They were none the wiser.

"Yeah, I'm not even sorry for the asshole...That's just what villains get!" Another person responded, and I clutched the straps of my backpack tighter.

Th..they can't be talking about Big Sis...can they..? Nobody could know about that...

With plenty of time to spare before class, I made a beeline for Aizawa's homeroom, knowing that I'd be able to squeeze information from the first years without seeming suspicious.
"(Y/N)! You're back!" Of course, Kirishima was the first to greet me; rushing over like an excitable puppy.

"Eijiro! Nice to see you!" I smiled as my default fox tail sprouted from the waistband of my skirt and wiggled about behind me. "Everyone seems to be bursting with gossip today! Do you know what they're on about?"

"You haven't heard?" A few of the other students approached us, and the boy who addressed me shifted his glasses up his nose. "There was a minor cell block commotion at Tartarus. Some of the lower level villains broke out and caused quite the ruckus!"

My tail stopped wagging in an instant, but I willed my second pair of animal ears to stay hidden. 
"Th..that's awful! Nobody was injured, were they..?" I hoped and prayed that the imprisoned members of the league were safe, but something told me I was going to be wrong.

"From the article I read...It sounded like one of the villains who attacked the training camp was hurt, kero. They're being strictly monitored at a hospital somewhere." A ravonette girl with rather big, bulging eyes noted, and Kirishima clicked his tongue.
"Yup! The news said it was that bastard who used his quirk to gas the forest! Serves him right!" I never thought I'd be angry with Kirishima. He was always so kind and understanding, but in that moment; his grin wide and bright, I wanted to sock him right in the kisser.

"H..how could you say something like that..?!" I snapped loudly, causing him and the others to flinch back. All eyes were on us, now, and my ears had popped out and flattened against my (H/C) hair. "Hiso...He's just a kid, isn't he?! E..even if he is a villain, that doesn't mean he deserved that!"

Careful, (Y/N)...You almost slipped up..!

"I kind of agree with your friend, Kirishima...It is a little harsh being so ecstatic about it..." The frog-like girl tapped her chin, but the red-head didn't look too convinced.
"I know he's a kid and all...but he pulled a gun on one of my bros! He deserves everything he gets!"

Kirishima Eijiro...you...you-

"You really are an asshole...if you think anyone deserves that!" If I had been in full animal form, my hackles would have been raised. I could see the shock and regret flash through his crimson eyes, but that served him right. I didn't even care about my own vulgar language, and I turned on my heels and stormed out of the classroom.

"(Y..Y/N), wait up! I-"
"Kirishima, I do understand your urgency to patch things up with your lady friend, but class is about to begin! Please sort this out after hours!" I heard the bespectacled boy lightly scold Kirishima as I marched down the hall, the opposite direction of my classroom. With fumbling fingers, I pulled out my phone and made my way outside before mashing one of my contacts.

"Ms. (Y/N), I didn't expect to hear from you during school hours. Is everything alright?"

"K..Kurogiri...I need you to do me a favour...please...and...I need you to not tell Dabi..."

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I knew Kurogiri wouldn't let me down. In no time at all he had managed to locate Mustard's location, and I was already lingering outside the hospital with my phone pressed against my ear.

"He is currently being monitored in room seven, in the post operation wing, located on the second floor. I do hope you will be careful, Miss. (Y/N)...He is heavily guarded from what I have managed to learn." Kurogiri instructed, and I nodded despite him not being able to see the action.

"I'm pretty sure I won't get caught...I just...I need to see him...Thank you, Giri..." I murmured, hanging up and shoving my phone into my pocket. I had skipped classes to do this, but I didn't care. Even though I had only known him for a short amount of time, I saw Mustard as a little brother. It had been my fault that he had been captured, and I needed to make sure he was okay.

Sucking in a deep breath, I did my token spin and morphed into an animal I hadn't really used before. Being a bumblebee bat was usually just something I reserved for mucking around and making people smile, but this time it would come in handy.

(Look at this wee lil bean)

Okay...all I need to do is fly up to the second floor...get inside and find his room...I can do this!

I was internally huffing and puffing as I began my rise to the higher floor, consciously keeping an eye out for large birds in case they wanted me for a late morning snack. Already mildly exhausted, I finally managed to find an open window and slipped inside, into a corridor.

Now...seven...post operation...

The wailing of newborn babies gave me a vague idea of where I was, so now I had to venture across the entire hospital to find the boy I so wanted to see. My quirk enabled me to lighten my colour, so I could blend in better with the stark walls, and I decided it would be easier to switch to a small mouse so I could dart along the skirting boards.

I almost died when a little girl saw me in one of the waiting areas, but she just gave me a small smile and watched me skitter on my way. Avoiding boots and wheels was trickier than I had hoped but, finally, I spotted the sign for the post operations wing.

I didn't even need to search for the room. Two very obvious, very armed guards stood stock still outside of the door, and I had to stop and rethink my strategy.

If I just slide under the door...it could be dangerous...I don't know if there's a guard inside, too...If they spot me, I'm as good as squashed!

I didn't really have much of a choice if I wanted to get in. There wasn't much of a chance the window inside would be open, and there were no other points of access. Whiskers quivering, I pressed myself as close to the wall as possible and began the most perilous part of my mission.

I stopped dead every time one of the guards shuffled their feet or made so much as a sniff, but I wasn't noticed at all. Flattening myself under the gap in the door, I immediately scanned the area for any sign of threat.

Nothing...okay...

Not a wisp of breath escaped me as I scaled the frame of the bed, and it all came out in a tiny, mousy gush as I laid eyes upon the boy I had came to see.

(First attempt at Clip Studio. Also doesn't help that Mustard doesn't have a good unmasked reference)

The risk of turning back into my human form was too great, even though I desperately wanted to throw my arms around Mustard and hold him close, so I opted for a smaller version of the cat I had first introduced myself as to the league.

Feeling my fur brush against his arm, the battered boy wearily lifted his lids, and his almond eyes widened as they laid upon me.
"(Y..Y/N)..?" His voice was a muffled croak coming from beneath the oxygen mask strapped to his face.

Yeah...yeah, it's me, Hisoka...

I mewed softly in response and nuzzled my nose against his cheek, careful not to irritate any of the gauze or bruising. In an instant; even though I knew it was painful for him to do so, I was wrapped up in quivering arms and held close to his chest, among wires and cables.

"Y..you idiot...Wh..why'd you come find m..me..?" Mustard whimpered, and I felt the first of many teardrops meld together with my fur.

Because I just had to...You have no idea how much I've missed you..!

I gave his chin a small lick with my coarse tongue, trying to comfort the young man who was trying so hard to make sure his sobs went unheard.
"It's...It's been so horrible...I d..didn't even d..do anything to get b..beat up...A..all I do is sit in my cell all d..day..."

His grip on me was tight, but I was fine with that. If I had been able to disable my quirk without risking it all, I would have been clinging to him in the same way. "I d..I don't wanna g..go back..."

He didn't speak again for a while. I just pressed into him and let him snuggle up to me, internally crying along with him.

It's all my fault...His suffering is all my fault..! I have to do something..! You know what..? Stuff it!

Pulling away, I crawled beneath the thin blanket and, completely aware of the risks, returned to my human form. Mustard just stared at me with rounded, bloodshot eyes, and I grabbed his hand in mine.
"I p..promise you, I'll get you out..." I whispered boldly. "I'll permanently join the league if that's what it t..takes to get them to help!"

"P..please..." Mustard's eyes spilled over with fresh tears, and his lips trembled as he tried to form a sentence. "...D..don't...don't fuck up your life t..too..." His words should have made me reconsider my declaration, but they had the opposite effect on my stubborn self. Seeing him broken and bawling upon a hospital bed had already sealed the deal I would inevitably seek to make with Shigaraki.

"As long as you're out of there...it's worth it..." I forced a plastic smile and wiped at my tear-stained face with my uniform sleeve. He went to respond in a panic, but I beat him to it. "I have to go...but I promise, Hisoka...somehow, I'll be getting you out of here..."

I didn't give the poor boy a chance to say anything more. Shifting back into the small, pale mouse, I tore myself away and blindly ran back out through the gap beneath the door.

Reckless didn't begin to describe the thoughts going through my head, but I wasn't about to go back on my word. I knew Dabi would rip me to shreds over it, but he had no say in the matter. The deal would be made between Shigaraki and myself, even if it had to be done behind the backs of the ones I cared about.

Mustard...Hisoka...even if I'll never be able to become a real hero...at least I would have been able to save you..!

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***I couldn't just leave my best boy to rot ;_;***