Aoi and Akane Kajiya are two twins who couldn't be less alike. While Aoi is intelligent, diligent, and well-mannered, Akane is athletic, pretty, and somewhat of an airhead. The two were constantly compared when they were children, but now, Aoi is a shut-in. The gap between them has grown wider over the years, but this all begins to change when Aoi starts going to school again.

Romantica Clock follows the two twins and their daily endeavors in school, life, and romance. With her will to never give up, Akane will certainly surpass him! However, despite being rivals, there is nothing stronger between them than the bonds of family.

Included one-shots: Volume 2: Kashino-kun wa Mahoutsukai Volume 3: Trick on the Chocolate Volume 4: Mahiro-chan no Volume 5: Dear Chloe Volume 7: Lemon wa Amanojaku Volume 10: Usagi Melancholy