Teiken Boxing Gym
Currently Kasai acts as a trainer of the Teiken Boxing Gym in Tokyo. He guided Toshiaki Nishioka whom he has coached for nearly ten years, to the world title in 2008, and was presented with the nineteenth Eddie Townsend Award that year. In 2011, Akifumi Shimoda trained by Kasai was crowned the world champion. Shimoda is the Teiken Boxing Gym's second boxer following Masao Ohba who became a world champion from a walk-in boxer with no experience. From 2012 through 2013, Toshiyuki Igarashi and Takashi Miura also secured the world titles under Kasai.