Hard Knock Days

"Hard Knock Days" is a song by GENERATIONS from EXILE TRIBE that served as the 18th opening theme for Toei Animation's One Piece (ワンピース).

Released as a single on August 12, 2015, it later appeared on the group's studio album Speedster. The single reached No. 1 on Japan's Oricon weekly singles chart. Shoko Fujibayashi wrote the lyrics, and SKY BEATZ, FAST LANE, and Chris Hope composed the music.