Hey guys I need help looking for a manga that I can’t recall the name of.

The beginning of it starts out that this boy is searching for his missing sister who I think everyone says is dead or ran away. While trying to look for her he goes to some abandoned hospital where he is attacked by some monster. I think they were called noise or something like that and they could infect people with some sort of disease. He gets rescued by an old childhood friend who is able to fight the monsters. He also finds a little girl who looks a lot like his missing sister. I think he calls the girl Nene or something.

Then again while searching for his sister he ends up getting infected by the monster and he childhood friend decides to give up his weapon that he uses to fight the monsters since it can stave off the infection and in doing so loses his life to save the boy. The boy then becomes able to fight the monsters and his hair changes color and he decides that with the power he has he can try to find his sister and decides to join the organization his friend was a part of. He then gets pairs with his childhood friends old partner and it goes on from there.

I want to say it started with World or was called something like end of the world or world end, but I for the life of me can’t find it.

Thank you guys so much in advance.

https://www.mangaupdates.com/series.html?id=1366