久保 晶子

Masaru's little sister and Yukinojou's childhood friend. She was the former manager of the boxing club when those two were still active members, even though she did not really enjoy boxing. The thought of her beloved brother and childhood friend "beating" each other always filled her with uneasiness.
Following the accident sending Masaru into coma, she harshly condemned Yukinojou, whom unable to bear this and the resulting situation moved to Kashima city. Short while later Shouko followed her, as she didn't intend to let him off the hook so easily.
After becoming heartbroken due to Yukinojou during the first game's course, and following Masaru's awakening, she came back to Ryouzuki and behaved a lot more cheerfully, as if she were a different person.
Nowadays, it seems she has completely gained back her normal cheerfulness and kindness. She's also a reliable girl who takes care of her incompetent older brother while also zealously studying.
According to Masaru, "she has an attractive face and figure, is keen-headed, has a gentle personality, cooks great food and an unrivaled little sister who loves cleaning."
Object of admiration for many in Ryuzuki Academy, and among other people Gonzou too has fallen for her at first sight.