Men's singles
2018 Keio Challenger
Champion	Yasutaka Uchiyama
Runner-up	Tatsuma Ito
Score	2–6, 6–3, 6–4

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

Draw

Finals

	Semifinals							Final
	1	Jordan Thompson	4	5
		Yasutaka Uchiyama	6	7
									Yasutaka Uchiyama	2	6	6
								7	Tatsuma Ito	6	3	4
		Cem İlkel
	7	Tatsuma Ito	w/o

Top half

	First round							Second round							Quarterfinals							Semifinals
	1	J Thompson	2	6	6
		P Gunneswaran	6	4	3			1	J Thompson	6	6
	Q	Hiroyasu Ehara	710	61	6			Q	H Ehara	4	2
		A Whittington	68	77	4										1	J Thompson	6	4	6
	LL	D Nguyen	6	6											5	S Robert	3	6	2
	WC	Yo Watanuki	2	4				LL	D Nguyen	5	0
	Q	Jumpei Yamasaki	6	1	3			5	S Robert	7	6
	5	S Robert	3	6	6																	1	J Thompson	4	5
	4	G Soeda	6	6																			Y Uchiyama	6	7
	WC	Kaito Itsusaki	0	2				4	G Soeda	77	6
		D Wu	6	77					D Wu	65	3
		Ze Zhang	4	65											4	G Soeda	6	60	3
		Y Uchiyama	6	3	6											Y Uchiyama	4	77	6
		H Hurkacz	4	6	4				Y Uchiyama	6	7
	WC	S Hazawa	6	4	77			WC	S Hazawa	3	5
	6	S-w Kwon	3	6	65

Bottom half

	First round							Second round							Quarterfinals							Semifinals
	8	D-h Lee	4	6	6
		T Pütz	6	4	3			8	D-h Lee	2	6	65
	SE	B Ellis	3	4					C İlkel	6	2	77
		C İlkel	6	6												C İlkel	77	6
		M Donati	711	2	5											T Kamke	63	2
		T Kamke	69	6	7				T Kamke	6	6
	Q	Y-s Chung	2	78	4			3	J Jung	4	2
	3	J Jung	6	66	6																		C İlkel
	7	T Ito	6	6																		7	T Ito	w/o
	WC	K Uesugi	2	3				7	T Ito	3	6	77
		J Kubler	6	1	6				J Kubler	6	3	63
		E Leshem	3	6	3										7	T Ito	6	6
		K Kravchuk	0	2											Q	H Moriya	3	3
	Q	H Moriya	6	6				Q	H Moriya	w/o
		M Purcell	3	67				2	J Millman
	2	J Millman	6	79

References

• Main draw
• Qualifying draw