Hair color: Red Eye color: Dark brown Was a class president and friend of Jae-Won in Elementary level. He's Jae-Won first crush. Though he moved to another place in elementary, he came back to the same neighbourhood in High school in the middle of second year. Has an elder sister. Yoon-Sung is smart, handsome and liked by almost everyone. He is full of himself though he is actually right about it. Apparently, he is the tallest among all characters in the manhwa.