Kuro is the second main character in this story. When you first meet Kuro, he seems like a genuinely happy, regular guy. He was diagnosed with clinical depression at the age of 12 and was put on medication for it. To keep his friends from worrying about him, he kept up his cheery personality. They go along with it, even though they know it's just an act. Kuro is very quiet and doesn't have the balls to stand up to anyone stronger than him, which makes him an easy target for both Shiro and Haruto's teasing. However he knows they're just teasing and is always able to brush it off.
Kuro's mother died while giving birth, which gave him this mindset that he was the one that ended his mothers life prematurely. Kuro is reminded daily of his mothers death by his father being unable to let go and his habit of bringing up that day.