"Happy ComeCome" centers around the life of a young girl named Hina, who moves to a small, picturesque town with her family after her father’s job transfer. The town is known for its unique tradition of hosting an annual festival called the "ComeCome Festival," which celebrates the arrival of spring and the renewal of life. Hina, initially feeling out of place in her new environment, gradually becomes involved in the preparations for the festival, which serves as the backbone of the narrative.

The story unfolds as Hina meets a group of local children who are deeply invested in the festival’s success. Among them are Taro, a spirited and determined boy who takes pride in his town’s traditions, and Yuki, a quiet but thoughtful girl with a knack for crafting intricate decorations. Together, they form a close-knit group, each contributing their unique skills and perspectives to the festival’s planning. As the days count down to the event, the children face various challenges, including disagreements, personal insecurities, and the pressure of living up to the town’s expectations.

A significant subplot involves Hina’s struggle to adapt to her new life while coping with the lingering sadness of leaving her old friends behind. Through her interactions with Taro, Yuki, and the other children, she begins to find a sense of belonging and purpose. The festival itself becomes a metaphor for growth and community, as the characters learn to work together, overcome obstacles, and celebrate their shared efforts.

The narrative also explores the town’s history and the deeper meaning behind the ComeCome Festival, which is rooted in a local legend about a mythical creature said to bring happiness and prosperity to those who honor it. This legend is woven into the children’s journey, adding a layer of mysticism and cultural richness to the story. By the time the festival arrives, the characters have not only grown individually but also strengthened their bonds, culminating in a heartfelt celebration that highlights the themes of friendship, tradition, and resilience.