2018 Keio Challenger – Men's singles

Yūichi Sugita was the defending champion but chose not to defend his title.

Yasutaka Uchiyama won the title after defeating Tatsuma Ito 2–6, 6–3, 6–4 in the final.

Seeds
• # 🇦🇺 Jordan Thompson (semifinals)

• # 🇦🇺 John Millman (second round, withdrew)

• # Jason Jung (second round)

• # 🇯🇵 Go Soeda (quarterfinals)

• # 🇫🇷 Stéphane Robert (quarterfinals)

• # 🇰🇷 Kwon Soon-woo (first round)

• # 🇯🇵 Tatsuma Ito (final)

• # 🇰🇷 Lee Duck-hee (second round)