AhJuicy

MC is the strongest person around while the world is breaking down. He saves a kid and takes him under his wings while being a teenager. Since he does hero stuff with his identity hidden (as J), no one realises they are making a teenager do all the work to save the world. Then he goes into a special portal. Once he is inside the thing changes, kills everybody but he survives and is send out 10years later or something. By then the world has changed "thanks to his sacrifice", so he decides that he isn't going to reveal he is back. It must have been pretty traumatising honestly to see how much better things got without him around, when he was so alone trying to save everyone before, despite being so young.

Meanwhile some other dude took his place as number 1. Said dude is the ML and same kid MC had saved. He was used in exemperiments by a messed organisation, doing shady things with a special drug. His job is to hunt the organisation, and he noticed MC is strong so he enrolls him, and realize he is J. Obviously since he was saved by J, he is very attached to him.

While hunting the organisation, MC learns that they trigger special abilities by experimenting specifically on people that went through trauma /survived a dangerous situation. He becomes worried about the kid he was taking care of, since he matches the criteria. But the kid in question is now number 1, so his background is fully hidden and MC can't find him.

Meanwhile, a high-school girl that can see alternative universe asks for help to MC because the world is ending. All alternative universes end and we don't know why. We slowly learn that the special dungeons might contain a clue and that the MC might be essential for that,since the special dungeons change when he gets inside.

I think that's the jist of it.

Thankk youuuu

not overreacting or something but I think I love you