With the win, the Swallows tied the Giants in number of wins but took first place in the Central League standings with a better win percentage.
Yomiuri, which lost its fifth straight game, fell to second place in the CL for the first time since April 10.
With one out and one on in the first inning, Inaba, who went 3-for-5, drilled a two-run blast to put the Swallows ahead. Petagine and Furuta then hit consecutive solo blasts to widen the lead.
All three dingers were off Yomiuri starter Koji Uehara (9-2), who gave up five runs on seven hits over five innings. He struck out eight.
Iriki, who was released by the Giants unconditionally at the end of last season, gave up one run and struck out six to pick up his league-leading ninth win.
Relievers Shinji Matsuda and Ryu Kawabata retired the side the rest of the way.
Giants right fielder Yoshinobu Takahashi belted a solo homer — his 16th of the season — in the second inning off Iriki for Yomiuri’s only run of the game. It was Takahashi’s seventh home run in the last nine games.
Dragons 4, Carp 2
Hirokazu Ibata singled home the game-tying run and scored the go-ahead run on Kosuke Fukudome’s infield single in the seventh inning as Chunichi beat Hiroshima at the Nagoya Dome.
Tigers 10, BayStars 6
Hanshin catcher Akihiro Yano smacked a three-run homer to cap a six-run first inning burst as the Tigers snapped their losing streak at three with a win over the BayStars at Yokohama Stadium.
With one out and the bases loaded, Makoto Imaoka singled home a run and Hiroshi Yagi followed with a two-run double.
With two out, Yano hit his fifth homer of the year to give the Tigers a six-run lead.
Hanshin starter Buddy Carlyle gave up one earned run in 52/3 innings for his fifth win.
Yokohama’s win streak came to a halt at four.
Hawks 6, Marines 4
Tadahito Iguchi had three hits and three RBIs, including a game-tying RBI single in the seventh inning, as Daiei came back from a three-run deficit to beat Lotte at Chiba Marine Stadium. It marked the Hawks’ first win in their last 10 games in Chiba.
With the Marines leading 4-1 in the sixth, Iguchi nailed a two-run clout to cut the lead to one run.
In the seventh, Iguchi sparked a go-ahead, three-run burst with a game-tying RBI single.
Daiei starter Keizaburo Tanoue (7-4) picked up the win despite allowing four runs over six-plus innings, while closer Rodney Pedraza pitched a perfect ninth for his 19th save.
Fighters 6, BlueWave 2 (10)
Atsushi Kataoka singled home the go-ahead run in the top of the 10th and Nippon Ham added three more runs in the inning as the Fighters beat Orix at Green Stadium Kobe.
Nippon Ham broke a 0-0 deadlock in the sixth when Michihiro Ogasawara belted a two-run clout off Orix starter Masahiko Kaneda.
However, in the ninth inning with two out and bases loaded, Yoshitomo Tani drew a walk for a run and pinch-hitter Akihito Igarashi hit a clutch RBI single that tied the game and took it into extra innings.