OVA episode bundled with fifth volume of manga.

Iketani missed an opportunity to see Mako-chan and hates himself for never calling to say he was sorry. By chance he runs into her 6 months later, and the situation is awkward. Iketani does not have time to talk at that moment, but both want to talk, so they arrange a second meeting. Iketani goes to the meeting place early, but an old man was left behind from an tourist bus, and asks Iketani to catch the bus for him. Iketani being a nice guy, so he can't say no.

High school student Issei Hyoudou is your run-of-the-mill pervert who does nothing productive with his life, peeping on women and dreaming of having his own harem one day. Things seem to be looking up for Issei when a beautiful girl asks him out on a date, although she turns out to be a fallen angel who brutally kills him! However, he gets a second chance at life when beautiful senior student Rias Gremory, who is a top-class devil, revives him as her servant, recruiting Issei into the ranks of the school's Occult Research club. Slowly adjusting to his new life, Issei must train and fight in order to survive in the violent world of angels and devils. Each new adventure leads to many hilarious (and risqué) moments with his new comrades, all the while keeping his new life a secret from his friends and family in High School DxD! [Written by MAL Rewrite]

Kumiko Yamaguchi is smart, enthusiastic, and ready to start her dream job as a math teacher at Shirokin Academy. But as her first day opens on atrocious students and cowering teachers, Kumiko realizes that the all-boys high school is a cesspool of delinquents with no intention of improving themselves. However, what her rowdy students don't know is that behind her dorky facade, Kumiko is the acting head of a powerful yakuza clan, and she has the skills to prove it! Capable of overpowering even the strongest of gangsters in seconds, Kumiko must keep her incredible strength and criminal influence a secret in order to keep her job. Unfortunately, with the vice principal constantly trying to get her fired and Shin Sawada, the leader of her class of delinquents, suspecting she's stronger than she lets on, Kumiko has a difficult teaching career ahead of her.