He has his own youtube channel, an official one. All his songs are there even predebut WINNER days. Hopefully, they'll update it. Go subscribed to his channel! Just search OfficialSeungyoon. ^^
Kang Seung Yoon is really the best singer I've heard in Kpop. You're a great singer if the listeners can feel the message of the song. I didn't know korean language but in this song you can understand and feel the message. You are really born to be a singer.