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 ends up in him being given custody of Kazuki's toddler son, Ryouta. Ryouta quickly comes under the impression that Touki's 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?

Matsuzawa Tomoya, a 21 cute and most capable undercover agent, has a mysterious past in which a man is covered in blood, but he doesn't want to share it with others. One day he's hired by a famous actress to spy on her son and report his affairs and from this point on things get complicated because her son's face is identical with the one Tomoya fears the most.

Trouble follows Kisanuki Shin around. Accidents and fights always seem to find him, but Shin’s quick reflexes and strong martial arts keep him relatively safe. As his bad luck would have it, Shin causes a car accident that totals an expensive Porsche, burdening him with a large debt. Unable to pay, Shin faces the prospect of dropping out of school to work—something he desperately wants to avoid. Due to his past delinquent behaviour, Shin was only admitted on the good graces and trust of the chairman’s representative; thus, Shin doesn’t want to trouble him or betray his faith.
Fortunately, Shin’s recent actions haven’t gone unnoticed. A popular model, Takami Ukon, witnessed both the car accident and a fight that Shin effortlessly dominated. He approaches Shin at school and proposes a deal: Shin protects Ukon from harm, and Ukon will pay the monthly installments on Shin’s debt. With barely any thought, Shin agrees to the deal. However, it turns out that Ukon was hiding his own secrets—he’s a strong fighter himself and also a magnet for trouble! It looks like Shin will be working hard for his paychecks.
[Written by MAL Rewrite]