"So Long!" is the 30th major single by the Japanese idol girl group AKB48. It is also AKB48's sixth cherry blossom-themed single, and its first single of 2013. This single was released in Japan on February 20 in four different versions.

Tomomi Kasai is a Japanese singer, actress and a former member of the idol group AKB48, belonging to Team A. She had a recurring role on Kamen Rider W as Elizabeth, alongside group member Tomomi Itano. Together, they make up the sub-unit Queen & Elizabeth.