The name's Kurogane Kei. He was living with his mum, three older sisters and one little brother until he left to follow Fuuta.
Fuuta and him met in elementary school year 6 and were in the same middle school, but Fuuta left for high school in another city.
Fuuta was his first friend after years of being alone because every friend he had would go away eventually, just like Fuuta.
After being so stressed out watching his brother got abused in the house he went away, but because he had nowhere else to go he followed Fuuta. Though he wanted to go away he still felt the pain of leaving his brother alone. But his brother was fine and said he can handle the sisters.