Keiichiro Yamamiya is a Japanese mixed martial arts fighter who was born on July 12, 1972 in Kanagawa, Japan. He is most famously known by his Japanese mixed martial arts fighting name which is KEI Yamamiya which is an abbreviation of his real name. 

During his time at the Era Kokushikan University, KEI began competing in wrestling. After graduating, he became a sports instructor and in 1995 he began his mixed martial arts career competing in the 1995 Pancrase Neo Blood Tournament. 

A year after entering the Pancrase Neo Blood Tournament, KEI made his professional MMA debut by defeating Satoshi Hasegawa by split decision on July 22, 1996 at the 1996 Pancrase Neo Blood Tournament event.   

Since making his debut in 1996, KEI has spent most of his mixed martial arts career competing in Pancrase where he has defeated fighters such as Chris Lytle, Ikuhisa Minowa, Denis Kang, Nate Marquardt and Chael Sonnen,