Formed in 2002 in Tokyo, Japan, the alternative rock and rap rock band Back-On consists of childhood friends KENJI03 (vocalist/guitarist) and TEEDA (rapper). They impacted the Japanese alternative and rap rock scene by blending heavy guitar riffs with hip-hop and pop-punk elements, famously creating theme songs for major franchises like Gundam, fairytale, and Eyeshield 21. Back-On was established in Adachi, Tokyo in 2002. Originally a standard rock outfit, the band went through several lineup changes over the years. By their 15th-anniversary and re-recordings like the album Flip Sound, the group streamlined into a core two-piece unit featuring the core creative partnership of KENJI03 and TEEDA.