A salaryman named Tsukasa Atsumi walks to his apartment from work in the dead of night. Without warning, he is ambushed by a giant hellish monster with an explicit desire to kill this unassuming young man. But when his life is seconds away from meeting a gruesome end, he is swiftly rescued... by a very attractive kunoichi with pink hair and a demeanor that's as sharp as her sword!

The young woman, Shizuri Ideura, reveals that Tsukasa comes from a long line of warriors whose blood attracts the attention of Youma, monsters like the very one that tried to kill him and she comes from a ninja clan established to protect people like him. Shizuri offers a proposition to the baffled salaryman: she will protect Tsukasa at all times... and he will provide food and a roof over her head.

But after being grilled on how soon he comes home from work, his savings, how is he at housework, and what kind of TV and game consoles he has, it hits Tsukasa that this kunoichi holds a deeper secret, one that's confirmed the second they arrive at his apartment and she suddenly pulls out a jersey and a pair of glasses:

This kunoichi isn't engaged in employment, education or training; she's a NEET!