When it comes to the fantasy MMORPG Cross Reverie, none can match the power of the Demon King Diablo. Possessing the game's rarest artifacts and an unrivaled player level, he overpowers all foolish enough to confront him. But despite his fearsome reputation, Diablo's true identity is Takuma Sakamoto, a shut-in gamer devoid of any social skills. Defeating hopeless challengers day by day, Takuma cares about nothing else but his virtual life—that is, until a summoning spell suddenly transports him to another world where he has Diablo's appearance! In this new world resembling his favorite game, Takuma is greeted by the two girls who summoned him: Rem Galeu, a petite Pantherian adventurer, and Shera L. Greenwood, a busty Elf summoner. They perform an Enslavement Ritual in an attempt to subjugate him, but the spell backfires and causes them to become his slaves instead. With the situation now becoming more awkward than ever, Takuma decides to accompany the girls in finding a way to unbind their contract while learning to adapt to his new existence as the menacing Demon King. [Written by MAL Rewrite]

When an extraterrestrial organism known as "Savage" attacks mankind, the only technology capable of combating the enemy is a weapon known as “Hundred.” A survivor of a Savage attack, Hayato Kisaragi is a teenager boasting the highest compatibility level with the aforementioned technology and as a result, is invited to master his skills at Little Garden, a prestigious military academy aboard a battleship. Over the course of his intense training for the battle ahead, he immediately attracts the interest of multiple female peers and gets drawn into a number of incidents as he tries to fight against the creatures that now inhabit Earth and threaten its safety. [Written by MAL Rewrite]

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.

Years ago, many magical "Artifacts" were stolen and scattered throughout the world. They fell into the hands of people who were not supposed to know of their existence, causing misfortune to those who abused their power. The Hoshisato family of magicians has special access to the Artifacts, and they take it upon themselves to return them to their rightful place. Despite her inexperience, Kana "Hatena" Hoshisato wishes to aid her parents Mamoru and Maeve in their quest, doing her best to improve. Meanwhile, her childhood friend Makoto Shiranui has come to their mansion to study magic under her father's tutelage as part of a promise they made years ago. Hatena is excited to see her friend again, only to be utterly disappointed when the person she thought to be a girl all these years turns out to be a boy, leading to a bitter reunion. Before long, Makoto comes to know of the Artifacts and the true identities of the magicians he admires. Unfazed, he continues to strive to fulfill his promises and stay true to why he learns magic—to ease the sadness of people around him and, most importantly, to become a person worthy of being Hatena's partner. [Written by MAL Rewrite]