O Thank U .. (Credit) Composed by 한길, D&T Lyrics by 한길, 마르코 Arranged by 한길, D&T Piano by 한길 Guitar by 정수완 keyboard by D&T Chorus by 한길 Mixed by 한길 @ Vamos Records Studio Mastered by 권남우 @ 821 Sound Mastering Executive Producer Vamos Records Music Producer 한길 Planning & Marketing 김지현, 안연주 Administration 김지현