Back-On (stylized as BACK-ON) is a Japanese rock band from Tokyo, Japan. They are recognized for creating anime and game opening themes such as the Tales of the World: Radiant Mythology 2 opening theme, "fly away"; Air Gear opening theme, "Chain"; Murder Princess opening theme "Hikari Sasuhou (fk Metal ver.)" and Eyeshield 21s "Blaze Line". etc., although they have also written ending themes for both anime and TV shows. These include "flower" and "a day dreaming..." for Eyeshield 21, and "Butterfly" for the late-night TV drama Shinjuku Swan, and most recently "Sands of Time" for the mobile robot TV drama Keitai Sousakan 7 and "Strike Back" for the continued run of the shounen anime series "Fairy Tail".

They formed a new band called BAReeeeeeeeeeN (バリーン, Barīn) with the 4-man band GReeeeN, produced by Jin (so 10 people = 10 e's) and their debut single "Ashiato" came out on October 1, 2008. The song reached No. 1 in the USEN and chaka-uta digital download charts.