Ore no Kioku ga nai Isekai no Danjon to Maho no Gakko Souta,宗太

The genius researcher and a highschool freshman, Haruyuki Kei, died after completing his research on a certain secret society.
Three gods appeared before him and asked, “Why did you research on this society? You lost your life because of it.” Since he gave a satisfying reply to the gods, they decided to give him a prize for breaking the code of the secret society.The prize is to be reincarnated into another world, without his memories. Now, living as Kazeyama Souta, he caught a glimpse of his past from his old world when he became 15 years old, and is now trying to find his lost memories and survive boarding school, while being tasked with killing the demon lord.