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After taking an insurmountable 3-0 lead in the best-of-five contest on Saturday, Japan's number four Sugita breezed past Indonesia's number one Christopher Rungkat 6-1, 6-3.
Then Uchiyama, who made a winning debut for the national team on Saturday when he and Tatsuma Ito took the doubles for a 3-0 lead, whipped Wisnu Adi Nugroho 6-1, 6-3 in the last dead rubber.
"I gained the momentum as I won my first match in the doubles after being called up for the first time for the national team. It gave me another chance to play the singles as we reached the second round," said Uchiyama, 20.
"I gained a lot of confidence that I won two matches in my first Davis Cup. It gives me further motivation to play better," he added.
On Friday, Ito and Go Soeda gave Japan a 2-0 lead in the opening-day singles without their ace Kei Nishikori, who was sidelined due to a left knee problem.
Japan's number three Ito defeated Rungkat 6-2, 6-2, 6-4 in the opener, while Soeda, fresh from winning the Maui Challenger in Hawaii two weeks ago, overwhelmed Nugroho 6-0, 6-0, 6-1.