INFINITE F (인피니트 F) is a sub-unit derived from the South Korean idol group INFINITE from Seoul, South Korea who is also active in Japan. The unit is made up of the members L, Sungyeol, and Sungjong. Their first song as a unit appeared on INFINITE's second album, "Season 2", and they officially debuted in Japan on November 19, 2014 with the single, "恋のサイン" (Koi no Sign). In December 1, they released korean first single album titled "靑" (Azure).