Mizuki Asami

The Tsukishima sisters' cousin from their mother's side. Mizuki's father, Isamu Asami, is a younger brother of Yōko Tsukishima. He is a world-renowned mountain climber and often travels around the world. As a result, Mizuki becomes an excellent climber too and has been raised overseas most of his life. However, he wants to at least finish his high school in Japan. Thus, he enrolls in Seishū and stays with the Tsukishimas. A kind and honest person, he is very popular with girls in Seishū, but he has stated that he is only interested in Aoba Tsukishima. He sees Yūhei Azuma as his rival on Aoba.

He is in Seishū mountaineering club, although he is always having his own activities as the club activities is below his expectations. He is often seen climbing tall structures, such as poles and school buildings, without any equipment. (Source: Wikipedia)