Manga Himekishi Ga Classmate!
姫騎士がクラスメート！(Japanese); A classmate is a princess knight! (English); Hime Kishi ga Classmate!; The Princess Knight is a Classmate!
Genre: Action , Drama , Fantasy , Harem , Seinen , Mature , Adult
After he and his entire class die on a field trip, Odamori accepts an offer from a mysterious man to be reincarnated. However his new job turns out to be that of a 'Slavemancer' with the power to dominate the minds of others and turn them into his toys, which he happily takes on. Soon however his evil actions lead to a Princess Knight (who turns out to be one of his previous, more popular classmates) being dispatched to apprehend him. But Odamori of course has something different planned for their reunion.