Shouko Kubo  

, 久保晶子

The little sister of Masaru is also Yukinojo's childhood friend. Although she did not particularly enjoy managing the boxing club where they were active members, her love for her brother and friend always made her uncomfortable when they fought each other. After an accident left Masaru in a coma, she strongly criticized Yukinojo, unable to bear the situation and its aftermath. As a result, she moved to Kashima city, where Shouko soon followed, determined not to let him escape so easily.