(Your POV)
Now that all of the sacred treasures were in one place, we decided to go to the stone of destiny, which was pretty anticlimactic if you ask me. It was a small stone overlooking a cliff. From what Dagda told me, the stone itself apparently yells with joy whenever a righteous ruler sets his foot on it, but there are a series of conditions that must be met when it comes to rulers. On top of that, the stone is broken because some idiot broke it. Due to everyone considering this treasure useless, no one with the right magic stepped up to help fix it, and I use ocean magic, which has earth magic in the mix.

On top of that Scathach decided to join us for whatever reason, and there was also this fellow who looked to be around my age here. His skin was an ocean green color, his eyes were a dull gold color, his hair was a dark cyan color and combed back, and his attire looked like that of a doctor's. Complete with a lab coat, glasses, and a stethoscope.

"Hey Grandfather, is this the guy?" The doctor-looking man was asking Dagda, who nodded. "So you're the immortal boy Father told me about, my name is Miach, son of Dian Cecht."

"I am (Y/N) (L/N), Ultimate Immortal of Kuoh Academy." I held out my hand for a handshake, and the two of us shook our hands. "I came here to see if you could do anything about my immortality."

"An odd request, but a wise one as well." Miach then pulled a letter from his back pocket. "I contacted Patecatl in what's now Mexico a little while back just in case someone wanted to remove Huitzilopochtli's blessing, and as a fellow medicine god, we exchanged notes. "

"By a little while back, he means 700 years ago." Dagda pointed out before pointing at the stone. "Anyways, Miach, could we wait until he fixes the stone? I wanna hurry up and get it fixed so Morrigan will get off my ass about it."

"Of course."

I walked towards the stone and crouched down and examined it, it indeed did have some cracks, but they were pretty miniscule. Despite that, there wasn't much magic coming from the rock, so I placed my hand on it and began reforming the rock bit by bit. When I was done, the rock looked the same, but Dagda told me to make sure by placing a foot on the top of the stone. I was confused by this, since I don't really see myself as a worthy ruler, but it's whatever. I placed my foot on the stone, and nothing really happened, not like I expected anything to happen. I looked at everyone, but I was caught off guard by Miach being right in front of me.

"Of course this didn't work, your body is broken." Miach pointed out as he circled my body. "In fact, it's only Huitzilopochtli's blessing that's holding you together, every injury you've ever had never disappeared. When did you get your head cut off?"

"The first, second, or third time?" I asked, and Miach looked at me with concerned eyes. "Say, how can you tell this?"

"I'm a god of healing, it's kind of my job to know these things." Miach informed me before a green magic circle appeared in his palm. "Now (Y/N), it's best if we hurry up and get this immortality removed anyways, but Huitzilopochtli wanted me to give you this letter."

"Hm?" I took the letter and opened it up to begin reading, one thing I noticed right away was how rushed the writing looked.

Dear (Y/N)
It's me, Huitzilopochtli, the guy who gave your blessing, and sorry about making you go through so much effort about all this. You looked like an interesting person, prioritizing your friends and all, even going as far as to die for them. I don't think there's many people like you around on this planet anymore, so I wanted to help you the best I could. Given how I'm busy feeding off my sister from the sun, there's not a whole lot I could do other than give you my blessing, or more like my curse. To try and make up for it...okay I can't really do much, but I'll do something!
P.S. I'm not attached to you because of that necklace your mom got you, she doesn't even worship me, I just thought you were interesting.
-Signed, Huitzilopochtli

"Good to know Huitzilopochtli isn't mad about me getting rid of his gift." I put the letter in my pocket. "So I suppose we're going to remove my immortality now?"

"Yes, but for your sanity, it would be best for you to be unconscious before I perform the ritual." Miach explained as he put on some surgical gloves. "Once your immortality gets removed, every single one of your injuries that your ability healed will come back. Due to my skills, I can heal all of them, but it'll still be painful."

"So when do I get knocked out?" I asked, then I noticed Dagda was missing and the sound of footsteps behind me.

"Right now." Dagda's voice could be heard behind me, and I was knocked unconscious by a giant club.

(Dream time)

My eyes opened to reveal me sitting on a dock, I looked around me to see the lighthouse I lived at, looking slightly different but still recognizable. It was a beautiful sunny day, and the tide was rather high, allowing me to dip my feet into the salty water while sitting on the docks. I felt taller and my hair felt longer for some reason, there was a goatee and mustache on my face, all of these features indicating aging. It was a calm ocean today, and covering the ocean surface were a variety of flowers roses, lavenders, daisies, marigolds, morning glories, magnolias, calla lilies, white roses, sun flowers, hibiscuses, hellebores, camellias, wisterias, chrysanthemums, and daylilies. Ironically, the first five always reminded me of Rias, Akeno, Koneko, Asia, and Xenovia respectively. The flower head bobbed upwards in a wave at random intervals, indicating a wave. I had always associated those flowers with the girls, but I wondered how the other flowers were for. It was always a secret dream of mine to open a flower shop, stupid, I know, but sometimes I like to think if things were different, then maybe I would have opened a flower shop. To my surprise, I wasn't alone on this dock, there were multiple figures, some were familiar some weren't. In fact, some of the figures were Rias, Akeno, Koneko, Asia, Xenovia, Sona, and Tsubaki. Though they all looked older as well, with a more mature aura radiating around them. If I had to guess how much older we were, I'd say we were around 7-10 years older than our current selves. Plus there were other female figures present, but I can't distinguish anything about them on the subject of their features, it was like my brain was preventing me from seeing them.

"(Y/N) Darling, have you thought of a name for our kids yet?" Rias, who was wearing a red sundress, asked as she hugged me from behind, and what caught me off guard about her question was that I noticed she had a slight bump around her stomach. "Not just mine, but also the rest of ours."

"So far, I've got nothing." I commented as I grabbed onto Rias' hand and kissed it, and for the record, I had no control over my body. "Sorry, I just want to put a lot of thought into names before I name the kids is all."

"That's perfectly fine." Rias kissed my cheek, and despite my body not blushing, I was extremely embarrassed. "Plus you've been busy with your flower shop and getting everything ready for the kids."

"It's still quite surprising that you have an interest in flowers (Y/N), considering you've always taken care of the lighthouse." Akeno also appeared to have a small bump, which I was able to see underneath her light purple kimono, please don't tell me I got all of the girls pregnant. "Maybe I should stop calling it the lighthouse and start calling it our home, since you agreed to marry all of us."

"Feel free to call it whatever you'd like, it's your new home afterall, unless you want to move." It appears I married all of these girls, evident by the rings on each girl's finger. "But for now, let us rest, it's all of our day off, the only one we have off together for the month, so let's enjoy it to the fullest."

I laid back on the dock, and Rias lay down next to me, clinging to my arm as we watched the fluffy clouds roll by. On my other arm was another woman, I couldn't distinguish any of her features other than a pink ribbon on her head. All of us lied on the docks, taking in the early noon sun and salty sea air. That's what my body was doing, but as for my mind, I was freaking out. How did I marry all of these girls? Why does the lighthouse look different? Why did I marry all of these girls? Am I able to make them all happy? Why did they all agree to marry me? Who are the figures I can't identify? Why is no one talking about the flowers in the ocean? Do I go to a church to get married if I'm a devil?!

These questions kept on piling on until I noticed that my head was resting on something soft, I looked up and saw a blurry figure, but I could make out nine golden fox tails. I could then feel my questions all fade away as I rested on the soft lap of whoever this woman was. A soft hand wrapped itself in my own, with our fingers interlocking one another's. As I began drifting away, I could hear each girl's voice say something to me, some of whom sounded unfamiliar. I opened my eyes to see who was talking, but it was now pitch black, and I was back to my normal self. I sat up to look around me, but I saw nothing but blackness, seven glowing flowers, and more unlit flowers.

"I miss you (Y/N)." The Rose glowed a red color, and for some reason, I pictured Rias hugging a pillow back home, trying to sleep.

"(Y/N), please stay safe." The lavender glowed a purple color, and I pictured Akeno at her bedside, brushing her black hair with a worried expression on her face.

"If anything happens to (Y/N), I won't forgive the person who did it to him." The daisy glowed a white color, and I imagined Koneko stress eating chocolates on the bed, despite the fact I've told her many times not to.

"Please god, please let (Y/N) stay safe." The marigold glowed yellow, and I pictured Asia at the foot of her bed, praying with a rosary.

"If (Y/N) comes back with even a scratch, I'll kill whoever hurt him." The morning glory glowed a blue color, and I pictured Xenovia lying on her bed, with both hands behind her head.

"(Y/N) will bring a great change in Hell, I just hope he lives long enough to see it." The hibiscus glowed gray, and I pictured Sona sitting at her desk, doing some paperwork.

"I may not know much about (Y/N), but I know that he's a good person, so I hope I get to see him again." The hellebores glowed a mint green color, I pictured Tsubaki sitting in a chair, looking at the full moon outside.

I know this may seem like a long shot, but I think I was actually able to see the girls in their current state, how was I able to do this? Astral projection? Cameras I didn't know I put up? I had no idea, but I honestly believe it was the first one because I had no better ideas. Or maybe this is just a dream. Still, I know all of these girls liked me, and now that I have a basic idea of what they're thinking, I will do my best to make them happy, even if they end up going out with someone else, I will support their happiness and goals.

(Dream end)

I woke back up to see a very tired Miach sitting on the grass I was laying on, I sat up to look around, and I noticed Dagda was asleep. Scathach was sitting on a bench nearby. Now that I looked at Miach, he looked slightly exhausted, his hair was disheveled, but my biggest concern was the dream I had.

"Am I a lonely pervert?" I asked myself, and Miach looked too tired to give so much as a single thought about this.

"How am I supposed to know, I met you a couple days ago, and you were unconscious most of those days?" Miach informed me, but then he told me I was unconscious for at least two days. "Oh yeah, did you astrally project by any chance? I hope that didn't scare you."

"Yeah, I did, how did you know?" I answered, and Miach began explaining the process my soul went through while the surgery was underway.

"At first, when you were just knocked out, you were pretty much dreaming." Miach explained, then things got weird. "Then when I removed your immortality, your body fell apart, so I had to force your body to enter a half awake/astral projection state to prevent you from dying."

"So my immortality is finally gone?" I looked at my hand, and it didn't look any different compared to how it normally did.

"Yes, you're a normal selkie/child of Danu now." Miach confirmed before telling me something I found interesting. "Though I found something odd about your blood."

"Am I something else?"

"What? No." Miach reassured me, and I was grateful I was only devil, selkie, and child of Danu. "It appears your blood has a unique trait to it that's simply called 'Adaptive Immunity'."

"Adaptive immunity?" I have never heard of this ability before, but it sounds pretty simple.

"Correct, your immortality was suppressing it however." Miach began explaining. "You see, adaptive immunity makes you immune to anything when over exposed to it for long periods of time, but it doesn't apply to offensive magic or weapons. For example, let's say you've been exposed to a poison, over time, you will eventually become immune to all poisons if you've been exposed to that poison long enough. This can also apply to certain magic, like time magic, telepathy, hypnotism, and other stuff along those lines."

"Wait, how was my immortality suppressing that ability?" I asked, because that seems like a bonus.

"Because your immortality doesn't heal you necessarily, it actually prevents change." Miach corrected my thought process. "Your immortality heals you whenever you get an injury, and enhances your body to prevent that injury from happening again for a while. Unfortunately, it also stopped your adaptive immunity from working, so you couldn't become immune to anything."

"Good to know, but I'm concerned as to what you meant when you said you were doing surgery on me for a couple days." I commented out of the blue, since I'm on a tight schedule, I want to know how much time passed since I came here."

"You've been unconscious for four days, since putting your body together perfectly takes time and precision." Miach then brushed a hand through his hair. "Why do you ask?"

"I have to get back to my friends, we're going to hell tomorrow to train." I explained as I ran towards Mule, which was stationed next to the sleeping Dagda. "I am grateful for everything you've done, but I must get going."

"By the way, what do your friends even look like?" Dagda appears to have woken up, I hope I wasn't the cause of that. "You speak pretty highly of them, but I have no idea what they looked like."

I decided to oblige since I don't have a reason not to, I pulled out my phone and showed him a group picture. It was a selfie of Issei back when he took my phone with all of us in the background. Koneko was holding up a peace sign whilst eating a piece of chocolate, Kiba was waving, Xenovia had no idea what was going on, Asia gave a photogenic smile, Rias radiated a serious aura from her desk, I was sitting on the couch next to Gasper, who was holding a dragon plushie, and Akeno was hugging me from behind.

"Those girls are cute, I suppose you don't mind if I date one right?" Dagda then flashed a smile, and I couldn't tell if he was joking or not, for some reason, Dagda actually stepped back after looking at my expression.

"Don't." I spoke solidly and in a slightly pissed off tone, then Dagda began waving his hands in front of him.

"Relax kiddo, I'm just making fun of ya, I know you like those girls." Dagda laughed as he pat me on the back, but I don't know why, but he gave me the impression that he was scared. "Also, feel free to take Solais, the Crimson Javelin, and the Cauldron of Plenty with you."

"Eh, why?" I tilted my head in a confused manner because these were his sacred treasures. "Don't these belong to you?"

"No they belong to the children of the danu, and there's not a whole lot of us left over, so I decided to give them to the strongest of us." Dagda handed me all three items. "Don't worry about the Stone of Destiny, we'll move it to your place."

"I sincerely thank you." I bowed before Dagda as I grabbed each item, with the Cauldron of Plenty being able to change its size to a small cup. "I hope to meet again in the future, but for now, I must get going."

"Later kid." Scathach told me goodbye, followed by Miach and Dagda doing the same while I ran towards the coast, summoning Jormungandr to help me get back to Japan on time.

(Dagda POV)

That kid was an interesting fellow.

I know Morrigan is going to have my head for this, giving some of the most powerful items in our possession to some kid, but that kid is a monster. Scratch that, monsters can't scare me like this kid did. Scathach seems to have noticed the fact I gave the four sacred treasures to (Y/N), and was curious to say the least, at least that's what I thought she was going to ask until she opened her mouth.

"So mind explaining how a third year high schooler from Japan managed to scare the great Father God Dagda?" Scathach asked, and I was grateful Miach passed out from exhaustion after operating on (Y/N).

"When I was joking with him, his eyes showed something..." I explained. "What lies behind those eyes of his is a wrath that I've never seen before. Not a wrath like an uncontrollable wildfire that lays waste to everything, instead, I see a wrath much like a calm, deep sea that swallows everything."

"So you're basically saying you stared into the abyss and the abyss glared back?" Scathach asked, and I nodded. "Shouldn't have fucked with him. Wait a minute, did you steal that quote from a Japanese manga?"

"Don't tell me how to live my life." I ordered, and Scatach refused to listen. "Either way, I think the quote suits him. He fears the strength behind his own wrath, so he suppressed it the best he can, but eventually it will boil to a point where he can no longer contain it against his enemies."

"Why didn't you help him with it?"

"Because he's scary, that's why."

(A/N: Just so in case you know where the quote is from, no, the MC is not turning into Meliodas, it would be more accurate to say he's more alike King, since he fights to protect, uses a spear, and is pretty versatile all things considered. Or maybe Ban would suit him better? Good friend, madlad, could fall under the magic rogue class... Yeah I'm just gonna say he's a mix of both.