| Men's singles | |
|---|---|
| 2017 Keio Challenger | |
| Champion |  Yūichi Sugita |
| Runner-up |  Kwon Soon-woo |
| Final score | 6–4, 2–6, 7–6(7–2) |
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.
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)| Semifinals | Final | ||||||||||||
| 1 | Yūichi Sugita | 4 | 78 | 6 | |||||||||
| Q | Blake Mott | 6 | 66 | 2 | |||||||||
| 1 | Yūichi Sugita | 6 | 2 | 77 | |||||||||
| Q | Kwon Soon-woo | 4 | 6 | 62 | |||||||||
| Tatsuma Ito | 4 | 4 | |||||||||||
| Q | Kwon Soon-woo | 6 | 6 | ||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 1 | Y Sugita | 6 | 6 | ||||||||||||||||||||||||
 A Velotti | 4 | 4 | 1 | Y Sugita | 6 | 6 | |||||||||||||||||||||
| C O'Connell | 1 | 77 | 3 | D Wu | 4 | 4 | |||||||||||||||||||||
| D Wu | 6 | 61 | 6 | 1 | Y Sugita | 6 | 6 | ||||||||||||||||||||
| B Kavčič | 4 | 6 | 6 | 7 | Z Zhang | 2 | 1 | ||||||||||||||||||||
| M Matosevic | 6 | 0 | 4 | B Kavčič | 4 | 65 | |||||||||||||||||||||
| WC | Yo Watanuki | 3 | 0 | 7 | Z Zhang | 6 | 77 | ||||||||||||||||||||
| 7 | Z Zhang | 6 | 6 | 1 | Y Sugita | 4 | 78 | 6 | |||||||||||||||||||
| 3 | D-h Lee | 5 | 78 | 1 | Q | B Mott | 6 | 66 | 2 | ||||||||||||||||||
 M Tepavac | 7 | 66 | 6 | M Tepavac | 3 | 4 | |||||||||||||||||||||
 F Škugor | 3 | 5 | Q |  B Klein | 6 | 6 | |||||||||||||||||||||
| Q | B Klein | 6 | 7 | Q | B Klein | 4 | 1 | ||||||||||||||||||||
| M Polmans | 4 | 7 | 6 | Q | B Mott | 6 | 6 | ||||||||||||||||||||
| PR |  C-M Stebe | 6 | 5 | 0 | M Polmans | 4 | 2 | ||||||||||||||||||||
| Q | B Mott | 6 | 6 | Q | B Mott | 6 | 6 | ||||||||||||||||||||
| 5 | G Žemlja | 2 | 3 | ||||||||||||||||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 6 | R Bemelmans | 6 | 6 | ||||||||||||||||||||||||
| SE |  L Harris | 3 | 4 | 6 | R Bemelmans | 4 | 6 | 3 | |||||||||||||||||||
| Y Uchiyama | 4 | 6 | 3 | WC | K Uesugi | 6 | 3 | 6 | |||||||||||||||||||
| WC | K Uesugi | 6 | 1 | 6 | WC | K Uesugi | 77 | 2 | 62 | ||||||||||||||||||
| J De Loore | 63 | 1 | T Ito | 63 | 6 | 77 | |||||||||||||||||||||
| T Ito | 77 | 6 | T Ito | 6 | 6 | ||||||||||||||||||||||
| H Moriya | 4 | 4 | 4 | G Soeda | 4 | 1 | |||||||||||||||||||||
| 4 | G Soeda | 6 | 6 | T Ito | 4 | 4 | |||||||||||||||||||||
| 8 | A Whittington | 65 | 6 | 6 | Q | S-w Kwon | 6 | 6 | |||||||||||||||||||
| WC | Sora Fukuda | 77 | 4 | 2 | 8 | A Whittington | 6 | 77 | |||||||||||||||||||
| Q | T Niki | 6 | 6 | Q | T Niki | 4 | 65 | ||||||||||||||||||||
| WC | Masato Shiga | 1 | 1 | 8 | A Whittington | 4 | 4 | ||||||||||||||||||||
| Q | S-w Kwon | 6 | 77 | Q | S-w Kwon | 6 | 6 | ||||||||||||||||||||
 J Jung | 3 | 62 | Q | S-w Kwon | 77 | 6 | |||||||||||||||||||||
| Z Li | 6 | 77 | Z Li | 65 | 3 | ||||||||||||||||||||||
| 2 | H Laaksonen | 3 | 65 | ||||||||||||||||||||||||
Andy Murray was the defending champion but decided not to participate.
Richard Gasquet won the title beating Gilles Simon in an all-French final, 6–2, 6–1.
Lu Yen-hsun successfully defended his title by defeating Yūichi Sugita 6–3, 7–6(7–4) in the final.
Michał Przysiężny was the defending champion but decided not to participate.
Rik de Voest was the defending champion but decided not to compete.
Defending champion Kei Nishikori successfully defended his title, defeating Pablo Andújar in the final, 6–4, 6–4, to win the singles title at the 2015 Barcelona Open.
Chung Hyeon was the defending champion but chose not to defend his title.
Yūichi Sugita won the title defeating Marco Trungelliti 6–4, 6–2 in the final.
Kei Nishikori was the defending champion but chose not to participate this year. Three-time losing finalist Julien Benneteau did not participate either.
Andy Murray was the defending champion, but chose not to participate.
David Ferrer won the title, defeating Steve Johnson in the final, 4–6, 6–4, 7–5.
Michał Przysiężny is the defending champion, but chose not to defend his title.
Roger Federer was the three-time defending champion, but lost in the semifinals to Alexander Zverev.
Novak Djokovic was the defending champion, but lost in the semifinals to Roberto Bautista Agut.
Yūichi Sugita was the defending champion but lost in the quarterfinals to Lloyd Harris.
Dudi Sela was the defending champion but chose not to defend his title.
Lu Yen-hsun was the defending champion but chose not to defend his title.
Florian Mayer was the defending champion, but lost to Roger Federer in the quarterfinals.
Alexander Zverev was the defending champion, but chose not to participate this year.
Yūichi Sugita was the defending champion but lost in the second round to Pierre-Hugues Herbert.
Jay Clarke was the defending champion but chose not to defend his title.
Stefanos Tsitsipas was the defending champion, but chose not to defend his title.
Mikael Ymer was the defending champion but chose not to defend his title.