Akira Oono is an ordinary working adult who manages the MMORPG Infinity Game. Fifteen years after creating the game, Oono decides to shut the servers down once and for all. However, as the clock strikes midnight, he somehow finds himself in the body of middle-aged Hakuto Kunai, Infinity Game's Demon Lord! Soon after his mysterious transportation, he witnesses the demon Greole chasing after a little girl named Aku. Although he effortlessly dispatches the creature, Hakuto is still concerned; after all, he does not remember creating the girl or the demon! Doubting whether he truly is in the world of his creation, Hakuto decides to investigate. Bringing Aku along as his guide and companion, Hakuto sets out on a journey to find out exactly who or what summoned him to this fantasy world—all while leaving chaos and destruction in his wake.

After gaining the title of the strongest warrior in the world, Peter Grill has finally proven his worth and is ready to take the hand of his beloved senior, the beautiful and innocent Luvelia Sanctos. Peter expects to have a healthy relationship with her, despite some objections from her father. Unfortunately, this dream quickly breaks apart as news of his grand victory spreads among the womenfolk of other races—ogres, orcs, elves, and others—some of them even vying for his seed to produce offspring blessed with his might. To avoid betraying the trust of his cherished Luvelia and causing a scandal, Peter strives to avoid other women's salacious advances. However, accomplishing such a feat with so many alluring women on his trail is easier said than done. [Written by MAL Rewrite]

When aliens known as the Oni threaten to invade the Earth, they promise to leave under one condition—a randomly-chosen human must win a one-on-one game of tag against Lum, the beautiful daughter of the Oni leader. The "lucky" person selected happens to be the lustful and unlucky high schooler Ataru Moroboshi. Given 10 days to attempt to grab Lum's horns, Ataru realizes how impossible the challenge is as he is faced with Lum's extraterrestrial powers. Motivated by a promise of marriage from his childhood friend Shinobu Miyake, Ataru manages to catch Lum off guard. He mistakenly grabs hold of her bikini top first, but he eventually achieves his true goal. Although the game is over, Lum misunderstands that she is the one whom Ataru wants to marry, and she decides to move in with him. The poor student constantly tries to shake off the clingy Lum while doing his best to reconcile with his desired fiancée. After Ataru's heroic feat results in such a disastrous outcome, it is questionable whether luck will ever be on his side.

Gen Kudou, a koto maker, believes that his delinquent grandson Chika would never understand the profoundness of the traditional musical instrument. In an attempt to make up for his naivety and understand the words of his late grandfather, Chika tries to join the Tokise High School Koto Club. Even though the club is in dire need of members, new club president Takezou Kurata is unwilling to easily accept Chika's application due to his bad reputation. Nonetheless, after seeing Chika's seriousness and enthusiasm, Takezou allows the problem child to join, along with koto prodigy Satowa Houzuki and three of Chika's energetic friends. Kono Oto Tomare! follows the merry band of musicians as they aspire to play at the national competition. [Written by MAL Rewrite]