Houjouin Seika♀

The daughter of the Hōjōin family whose company are rivals to Arima. Although she is initially neutral towards Teppei, once she finds out he is an Arima, she immediately dislikes him due to her family's longstanding antipathy for Teppei's grandfather (Many years previously, Teppei's grandfather was a workaholic and his lonely grandmother had an affair with Seika's grandfather which resulted in Isshin throwing his wife out of their house and his cutting ties with the Hōjōin. More recently, he refused to sell Seika's fashions in any of his group's stores).

Seika has a loud and forthright nature. She is the 'Club Representative' of the 'Society Club' and reserves the right to limit membership to those students who satisfy her conditions to join the school's most elegant and exclusive club.

Outside of school, she is a very popular model and one of the most gifted young fashion designers in all of Japan. Despite her initial dislike for Teppei, she falls in love with him due to his tenacious nature. However, she is uncertain how Teppei will react and is mostly quiet about it.