"Raku Raku" is a manga series that centers around the daily life and romantic entanglements of its protagonist, a high school student named Raku Ichijou. Raku is the heir to a yakuza family, a fact he tries to keep hidden from his classmates to maintain a normal school life. His life takes a dramatic turn when he discovers a pendant he has worn since childhood is actually a key to a mysterious lock. This pendant is tied to a promise he made ten years ago with a girl he cannot remember, and it becomes the catalyst for a series of romantic complications.

The story introduces Chitoge Kirisaki, a beautiful and spirited transfer student who quickly becomes Raku's fake girlfriend as part of a mutual agreement to avoid unwanted romantic advances from others. Despite their constant bickering and apparent dislike for each other, their relationship grows more complex as they spend time together. Chitoge also possesses a pendant identical to Raku's, leading him to suspect she might be the girl from his past. However, the situation is far from straightforward, as multiple girls in Raku's life—each with their own unique personalities and connections to him—also claim to hold the key to his past promise.

Among these girls is Kosaki Onodera, Raku's shy and kind-hearted classmate, whom he has harbored feelings for since middle school. Kosaki also has a pendant, further complicating Raku's search for the truth. Other significant characters include Marika Tachibana, a persistent and assertive girl who is deeply in love with Raku and openly pursues him, and Seishirou Tsugumi, a skilled bodyguard working for Chitoge's family who develops her own feelings for Raku.

As the story progresses, Raku navigates a web of romantic misunderstandings, comedic situations, and heartfelt moments, all while trying to uncover the identity of the girl he made the promise with. The series balances humor, romance, and drama, exploring themes of love, friendship, and self-discovery. The interplay between the characters and their evolving relationships drives the narrative, creating a dynamic and engaging storyline that keeps readers invested in Raku's journey to find the truth about his past and his heart.