Takuma Sakamoto, an elite player with social issues, finds himself transported to the virtual world of his favorite MMORPG, Cross Reverie, as the fearsome Demon Lord Diablo. Summoned by two maidens in need, Rem and Shera, Takuma becomes their unexpected master when a spell meant to enslave him backfires. Struggling with social anxiety, Takuma embraces his Diablo persona and uses his immense power and knowledge of the game to navigate this new world. Together with Rem and Shera, he embarks on a quest to remove their slave collars while helping them confront their personal challenges. In a world where Takuma's virtual life becomes a reality, he must learn to adapt as the formidable Demon King Diablo. This manga adaptation is based on the light novel series "How NOT to Summon a Demon Lord" by Yukiya Murusaki.