Tsuchiya Narumi, a boy who left his parents when he entered high school, decided to stay at the house of his distant relative's older sister, Kanako Chiaraijima.
Kanako works hard as a successful career woman, but the face she shows at home seems to be a little different...?!

I'm the only one who knows her true face?
Beauty x Carelessness = The Best!
A comedy limited to the living room!!

In order to ensure the protection of a 14-year-old girl stuck in a succession war between Mafia clans and other powerful conglomerates, the serious inspector Hatori is forced to collaborate with the whimsical Kuroumaru Wakatsuki, a legendary assassin, known under the name of "Black Dog."

Will this poorly matched duo get along enough to pull young Mana from the clutches of the horde of killers on his heels?

Thus begins an infernal chase on the trail of the most fearsome assassins in the world!