Koike Teppei is a Japanese actor, singer, and musician best known as one half of the pop duo WaT, alongside Eiji Wentz. Born in 1986 in Osaka Prefecture, Koike gained recognition for his melodic voice and heartfelt performances that blend J‑pop sensibilities with acoustic warmth. Following WaT’s debut in 2005, their youthful sound and emotional sincerity earned them national popularity and multiple music awards. In addition to his musical endeavors, Koike has built a successful acting career, continuing to captivate audiences across both screen and stage.