12 Beast

The story follows Eita Touga, a video game-addicted high school student who happens to be the reluctant heir to a prestigious ninja dojo. Eita prefers digital dating simulators over real life, but his world changes when a harpy girl named Aero breaks into his dojo. She teleports him to an alternate dimension called Re-Verse to help defend its mythological denizens against an invading empire of giant robotic monsters known as Gigas. Armed with a magical gauntlet, Eita must embrace his ninja training alongside various fantasy creatures.