A legendary mercenary Log Killer, once feared as a killing machine on the battlefield, has arrived in Japan. He has taken on a new name: Ryusei Nogawa.

His mission: to "raise a baby."

But Nogawa, who has never known a peaceful, quiet life, is struggling mightily with parenting for the first time!? To ensure the healthy growth of the mischievous Hoshina-chan, he must "legally" eliminate any dangers that come his way!