One summer ten years ago, you made a promise to a girl to marry her once they reunite. The promise girl exchanged a pendant with her and held on to a key that would unlock it once they meet again. Ten years had passed and you has no memory of the girl's name or what she looks like but remembers the promise you made.

After you started his fake relationship with Chitoge Kirisaki arranged by your father who is a Yakuza gang leader and her father who is a Mafia gang leader to make both side not fight each other for the peace of the Bonyari city, you encounters a series of events where you learns that Chitoge Kirisaki, Kosaki Onodera, Marika Tachibana, and Yui Kanakura all possess keys that are connected to his pendant and that they all met each other ten years ago. They all seemed to have made a promise with a boy ten years ago too. This makes all four of the girls be the possible promised girl until Yui returned to you and confirmed yourself that she is not one of the possible promised girls, despite having a key.

You are also the heir to the Yakuza family as the only son but wishes to not take the position, even if you are urged by the members of the gang.

Anyway, snap back to the reality, you just wake up from a weird dream, heard some usual chaos noise from your house and some members of the gang, these guys never make the house stop bustling...

"Bocchan, Ojō-sama is waiting for you."

Still wearing that sleeping kimono, you open the door with a sleepy face and the scene in front of you make you stun for a while

Chitoge: Good morning, "darling". Sorry it's a bit of a surprise, but can we go on a date?

Beside "your girlfriend" is Claude, a strict and dangerous person who always protect her like a body guard, It's best not to let him, his Mafia members and your Yakuza members not know the truth, right? So you took Chitoge out on your day off for a couple date and of course there will be secret tracking from some of you guys members...

Chitoge: Why I have to date a beansprouts like you...?