Shuyo, Omukae no Jikan desu

"Is my adorable little nephew the reincarnation of the demon king Lucifer?!"

Chris, a picture book author, takes in his nephew after the loss of his brother and sister-in-law during an accident. Noah is a strange and eccentric child with the ability to communicate with animals. One morning, overwhelmed with his new parental situation, Noah jumps into the road?! However, the person who saved Noah before it was too late was Harvey-sensei, the nursery school teacher, a demon with black wings and horns!! Revealing his true identity, the demon kneels down saying, “I have come to take you back, Lucifer-sama.”, announcing that Noah is the reincarnation of the demon king?!

(Source: Tokuma Shoten, translated)

Note: The chapter count includes an extra.