The Isekai Illusion Theory

After death, Theo Moretti learns his theory was right: the brain creates an endless illusion shaped by belief. Choosing to be reborn in a “realistic” fantasy world, he vows to succeed without cheats, only to die almost immediately. Desperate to continue, he takes his single hidden gift: resurrection. Now, this shy teen must survive in a brutal world, joining the chaotic Suicider group, Grimwerod. With nothing but knowledge and his secret immortality, Theo fights for his place among his first real friends, while dreading the truth that they only exist inside his own mind.