See main article: 2015 Keio Challenger.
The Keio Challenger is a professional tennis tournament played on hardcourts. It is currently part of the ATP Challenger Tour and the ITF Women's Circuit. Having been held in Yokohama, Japan since 1999. In 2015, Taro Daniel won the men's singles title, defeating Go Soeda in the final 4–6, 6–3, 6–3.