High School DxD

Caught with a severe fever, Tobio Ikuse, a second-year high school student, was forced to miss his school trip on a luxury liner with his schoolmates. Four days later, Tobio hears the news about the disappearance of the teachers and second-year students from his school, and it devastates him. A few months after the incident, Tobio, having slowly recovered from the sudden loss of his friends, accidentally encounters one of them again. Chasing after his missing friend Sasaki, Tobio finally manages to catch upto him, but is shocked to see Sasaki alongside a Lizard Monster who attacks him together with the monster. Cornered by the monster, Tobio is rescued by another survivor of the missing luxury liner, Natsume Minagawa, who then hands him an egg before parting ways. Later that night, Tobio finds himself under attack, again, this time by two people with monsters. Amidst all the ensuing chaos, out of Tobio's shadow, came out a Puppy that rescues him. After fending off the two monsters, Natsume once again approaches Tobio before finally deciding to take him to their hideout.

I’m going to make this school my harem! When a cute girl asks Issei out, he believes his twisted fantasies are finally coming true. Too bad the girl sprouts a pair of black wings and stabs him with a spear on their first date! Saved by his school’s number one beauty, Rias Gremory, Issei is transformed into a demon and made her servant. Issei hopes to rise through the ranks of demonkind to grow powerful enough to create his harem, but in a city with fallen angels and insane priests, he’ll be lucky if he can live long enough to do it! (Source: Yen Press)

Spin-off of High-School DxD that deals with the lives of two cute girls in the group, this takes place after Chapter 10 of the main manga series

Manga adaptation of the short stories found in the eight volume of the light novel.