“Babuba, Babubabubabubabu!?” (Am I going to be a baby!?) Thoth, a legendary assassin in the underworld, was sold by his parents at a young age and was raised strictly as a killer, so he never knew the love of a family he lacked. Suddenly, he saves a cat and dies, but after his death, he’s destined for hell for taking countless lives. However, because of one good deed—saving a cat—he's allowed to be reincarnated and is born again as a royal princess, Patricia. Then, God commands him to save the royal family—his family. He was supposed to be reborn as a helpless baby, but his assassin skills haven’t faded, and he continues to battle killers one by one. Gradually, feelings of wanting to protect the royal family members who love each other unconditionally just because they are family...?