The Pacific League-leading Fighters won their third straight game to move a season-high 14 games above .500.
Fujii (5-4) allowed three hits, all singles, struck out three and walked one at Sapporo Dome. Yuta Omine (2-5) took the loss.
Shota Ono had an RBI double and Kensuke Tanaka a run-scoring single in the fourth before Yoshio Itoi and Terrmel Sledge hit solo homers for a 4-0 lead in the fifth. Saburo Omura hit a three-run homer to move Lotte within one run in the seventh.
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Lions 4, Buffaloes 1
At Seibu Dome, Takayuki Kishi and three relievers limited the damage to one run and seven hits as Seibu beat Orix for its fourth win in six games.
The tiebreaking run scored from third on an errant throw by catcher Fumihiro Suzuki to third on a failed squeeze bunt. Sumitani Ginjiro added an RBI double and Takumi Kuriyama a run-scoring single, both off Chihiro Kaneko (8-6), for a 4-1 lead.
Kishi (10-1) allowed one run on six hits over five innings and notched double-digit wins for the third year in a row.