Unaired anime episode bundled with the limited edition of High School DxD DX.1.

Takuma Sakamoto is a hikikomori gamer who is mysteriously transported to the virtual world of his favourite MMORPG, Cross Reverie, with the appearance of his own character in the game, the Demon Lord Diablo. The two young girls who summoned him, the pantherian Rem and the elf Shera, attempt to use a spell to make Takuma their servant, but due to his magic ring with the ability "Magic Reflection", the spell rebounds, and both end up with magic collars stuck on their necks, thus becoming his servants instead. With a serious case of social anxiety, Takuma decides to act like his character while interacting with others, and makes use of his high stats and vast knowledge of Cross Reverie's lore to survive in his new environment, traveling along with Rem and Shera to look for a way to remove their slave collars, while helping them with their own personal issues that led them to summon him in the first place.

Torako Koshi is the epitome of perfection. With her peerless beauty, top-notch grades, and position as student council president, her popularity in school is unrivaled. However, she harbors a dark secret—she was a delinquent back in middle school—and this is something she conceals to the best of her abilities. Unfortunately, when she meets the mysterious deer girl Noko Shikanoko, Torako's hidden shame is constantly on the precipice of being exposed due to Shikanoko's rather weird antics. To maintain the reputation she worked so hard for, Torako must go along with Shikanoko's whims, even going so far as to become president of the newly established Deer Club. All her efforts will be rewarded if she can prevent the menacing doe from accidentally blurting out damaging details about her personal history that will undoubtedly unleash Torako's greatest nightmare.

A long time ago, the ancient saviors of humanity founded a village as their haven, with their descendants said to assist humanity in times of extreme chaos. This village, Kunlun, is located just beside the infamous "Last Dungeon"—a place where monsters of unimaginable strength reside and which serves as the hunting grounds for Kunlun residents. Despite being accustomed to defeating powerful enemies since childhood, Lloyd Belladonna regards himself as the weakest in his village in terms of magic, strength, and intelligence. Even so, to fulfill his desire of becoming a soldier, he goes to the Kingdom of Azami to enroll in its military academy. However, as someone whose upbringing defies common sense, Lloyd's innate power might just prove to be the key to end the crises enveloping the kingdom! [Written by MAL Rewrite]