Kazuya Watari, an ordinary high school student, finds his life thrust into chaos after stumbling upon a shapeshifting protector sworn to defend Earth. Bound by secrecy, he’s forced into a cohabitation pact with her—a pattern that repeats as more girls with concealed supernatural roles invade his world. A runaway magical princess declares him her destined husband upon exposure. A stoic ninja fugitive shackles herself to him, bound by clan honor after he aids her escape, her icy demeanor thawing into reluctant admiration. An alien mimic, whose powers manifest through cosplay, stumbles through earnest but perpetually interrupted confessions. A cryptic priestess weaves herself into his household without explanation, her spiritual aura a constant enigma.

Tensions flare as rivalry and jealousy fracture the group, particularly targeting the fiercely territorial protector, who sabotages rivals while masking her dual life. Skirmishes escalate into explosive clashes, with some girls vowing vengeance against her alter ego. The household oscillates between absurd comedy and high-stakes drama as alliances shift and missions collide.

Through shared trials, hostility morphs into fragile trust and simmering romance. The ninja begrudgingly accepts their fated bond yet fumbles to voice her feelings. Others vie relentlessly for Kazuya’s attention, their affections clashing like swords. Amid the chaos, a mysterious entity occasionally gifts him transformative heroic powers, observing the fray with detached curiosity. Kazuya’s existence centers on balancing these colliding worlds—mediating supernatural crises and navigating the storm of competing hearts, secrets, and destinies under his roof.