Yoshihito Ishii's seventh-inning pinch-hit single broke a 3-3 tie and helped extend the Central League-leading Yomiuri Giants' unbeaten streak to seven games.
Ishii, signed by Yomiuri after he was released last autumn by the Seibu Lions, singled home Takayuki Terauchi from second with two outs in the seventh and the Giants held on to beat the Tokyo Yakult Swallows 4-3.
"I was really nervous, coming to bat in front of so many fans," said the left-handed-hitting Ishii, who began his career with Yokohama in 1997. "My teammates created that scoring opportunity, and I just wanted to do my best."