Season 1

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!

La storia segue le vicende di Issei Hyoudo, uno studente del secondo anno delle superiori goffo e voglioso, il quale desidera crearsi un suo harem personale. Tuttavia al suo agognato primo appuntamento esso viene ucciso. Issei si reincarna in un demone di basso rango, e da quel giorno in poi sarà il fedele servo di Rias, un demone di alto rango, nonché la ragazza più bella della scuola. Ogni demone di alto rango ha la possibilità di avere un intero team al suo servizio. Riuscirà Issei a diventare un demone di alto rango e a realizzare il suo desiderio?

兵藤一诚是一个就读于女生占多数的私立驹王学园的高中二年级生。就读这个学校的目的只有一个——组建自己的后宫。实际上却是，别说是后宫了，在学校被女生称作变态，当初的梦想变成了妄想…… 就在这时，一件奇怪的事情过后一诚也有了女朋友并进行了初次约会。傍晚在公园，女朋友在渐渐靠近一诚……“难道是接吻？不会是更加……”兴奋于工口妄想的一诚被女朋友微笑着告知：“能不能请你死一下？” “突然就被人生中第一个女朋友杀了！为什么！？”心想着的一诚在自己房间的床上醒来了。然而旁边，红发的美少女、学园的前辈莉亚丝·吉蒙里全裸（巨乳）地在熟睡着！？“我还没死？为什么莉亚丝学姐会在这？为什么裸体？话说已经看到学姐的胸了！？” 听完了莉亚丝的说明的一诚知道了这个世界还有恶魔的存在。莉亚丝自己也是恶魔，同时是把一诚复活并转生为恶魔的人。而且代价居然是要作为莉亚丝的下仆恶魔永远服从她……惊愕的事实、荒唐无稽、混乱的一诚。“下仆恶魔？莉亚丝学姐的下仆？就是说有机会揉到莉亚丝学姐的胸？”因为天生的工口力量和乐观态度，一诚接受了这一现实。 重生的一诚作为下仆恶魔的学园生活拉开了序幕！没错，为了某一天能拥有自己的后宫！？