The strongest saint in the former human world, betrayed by her comrades and killed, and summoned to the demon world, somehow became a small yellow "chick." She begins her second life to repay the ruthless demon king who gave her a fluffy appearance, but—she runs wild on errands, punctures a chick-shaped hole in the door, and innocently overkills the Demon Knights as a training partner! They were supposed to live as relatives, but with the spirit of becoming a baby, they only lead to catastrophes. And yet, the supposedly merciless Demon Lord blushed and declared himself a father!? "...I'll raise you myself (how adorable and energetic! I have to protect you!)"