La historia se centra en Kai, una melancólica estudiante de secundaria cuya vida cambia después de conocer a Lu, una sirena.

La historia se desarrolla en Lawless, una ciudad próspera gracias a la venta en el mercado negro de licor fabricado ilícitamente. Avilio regresa a Lawless después de un tiempo fuera, tras el asesinato de su familia en una disputa mafiosa.

Hanabi Ayase and her best friend, Yui Aoi, are 6th graders in school. When Hanabi is chosen to work with Yuuto Takao for an upcoming test, she begins to fall in love with him and they both start dating. Yui also falls in love with Kazuma Hiyama, after he protects her from a classmate who talked about Yui behind her back, and they start dating as well. But with physiological changes and more and more obstacles in their love lives, will Hanabi and Yui overcome everything and find true love at the age of 12?