He is like a brother to Touko. He's from a family who adopted Touko. He is actually a 1st year in high school who likes to play with multiple girls at the same time.

Spoiler

He likes girls with dark feelings or like he said "dangerous". When meeting Miu in "Parumiere (パルミエーレ)" book, he began his long term relationship with Chia. He has been another person besides Himekura that giving information to Touko's involvements to events using his way of "girlhood" until "Romancie" book. He forced Konoha to write novel or Touko will "disappear". He claims that he's the reincarnation of Takumi Suwa, his father who fell in love with Touko's mother (says that she's his first love) and responsible for giving poison for both Touko's parents to die in car accident. He's like his father, who fell in love with multiple women who is older.