뻔하다고 치부될지언정 변하지 않을 소중한 마음들을 위해. 01 HAPPY END Lyrics by 김필 Composed by 김필, 623 Arranged by 623 Background Vocals by 김필 Drums by 신승규 Bass by 최인성 Piano and Synth by 김영호 Electric Guitar by 김동민 Recorded by 박정호 at WAKEONE Studio, Titan Recording Studio Digital Editing by 박정호 at Bliss Music Mixed by 오형석 at Titan Recording Studio Mastered by Chris Gehringer at Sterling Sound, USA