Kaisei Yui (油井 快晴, Yui Kaisei; born 6 February 1996) is a Japanese track and field sprinter who specialized in the 400 metres. He competed in the 4 × 400 metres relay at the 2014 World Indoor Championships without qualifying for the final.
Source: “Kaisei Yui”, English Wikipedia (CC BY-SA 4.0), excerpt