Popular writer Itsusu Touki learns about the death of his estranged twin brother, Kazuki, and rushes to help in any way he can. This eventually results in him being given custody of Kazuki's toddler son, Ryouta. Ryouta quickly comes under the impression that Touki is his father, but this is the least of the young man's problems, as he struggles to overcome the trials of suddenly finding himself a single parent.

Ryouta begins to attend the nursery where Kuramoto Yuuji (nickname: Nacchi) is the caretaker. Nacchi's bright and cheerful disposition is an instant hit with kids and parents alike, and Ryouta loves him. But what does Touki think of this sunny guy, his polar opposite in terms of personality?