2017 Keio Challenger – Men's singles

Taro Daniel was the defending champion but chose not to defend his title.

Yūichi Sugita won the title after defeating Kwon Soon-woo 6–4, 2–6, 7–6(7–2) in the final.

Seeds
• # 🇯🇵 Yūichi Sugita (champion)

• # Henri Laaksonen (first round)

• # 🇰🇷 Lee Duck-hee (first round)

• # 🇯🇵 Go Soeda (second round)

• # Grega Žemlja (first round)

• # 🇧🇪 Ruben Bemelmans (second round)

• # 🇨🇳 Zhang Ze (quarterfinals)

• # 🇦🇺 Andrew Whittington (quarterfinals)