Masahiro Tanaka’s winning streak has come a long way since his loss to the Seibu Lions last season.

Back on the mound where he last tasted defeat, Tanaka brought the streak around full circle, just in time to write his name in the record books.

Tanaka threw eight strong innings, got a big assist from Ginji Akaminai’s tiebreaking home run in the eighth, and won his Japanese baseball-record 21st straight decision in the Tohoku Rakuten Golden Eagles’ 3-1 win over the Lions on Friday night at Seibu Dome.

“More than anything, I’m pleased that we took the first game of the series,” Tanaka said.

The victory gave Tanaka (17-0) sole possession of the longest winning streak in Japanese baseball history, moving him past former Yomiuri Giants pitcher Kiyoshi Matsuda, who had a 20-game streak over the 1951 and 1952 seasons, and Kazuhisa Inao, who won 20 straight in 1957 for the Nishitetsu Lions.

“Inao-san was great in his era and Tanaka is great,” Rakuten manager Senichi Hoshino said. “But he’s (Tanaka) done it in this era, where you can give up a home run to anyone in the lineup.”

“Ma-kun” is 21-0 with a 1.02 ERA during the streak and hasn’t allowed more than three runs in any of his last 27 starts.

“It’s due to the efforts of the entire team,” Tanaka said. “I’d like to look back at it when the season is over.”

Tanaka’s last loss came Aug. 19, 2012, when he allowed six runs on 10 hits in a 6-2 loss to the Lions at Seibu Dome.

He bounced back by throwing 10 scoreless innings in his next start, a 1-0 win over the Hokkaido Nippon Ham Fighters on Aug. 26, which marked the beginning of his current win streak.

“I’ve run out of things to say to praise him,” Hoshino said.

Tanaka allowed one run on five hits, struck out 10 and walked one on Friday to improve to 17-0 with an ERA of 1.20 this season. He also added another game onto the NPB record for consecutive wins to start a season, which he set last week.

“He’s been super special, good and great this year, said Eagles reliever Takashi Saito. “It’s unbelievable.”

With scouts from a number of MLB teams, including the Cleveland Indians, San Francisco Giants, Atlanta Braves, Los Angeles Dodgers, San Diego Padres, Washington Nationals and Boston Red Sox, and New York Yankees assistant GM Billy Eppler, in attendance, Tanaka dipped into nearly every part of his arsenal, blowing by some hitters with a fastball that topped out at 148 kph, and utilizing a solid forkball and slider in other situations, with a few cutters and curves mixed in for good measure.

“He’s the real deal,” said Eagles closer and former New York Yankee Darrell Rasner. “I’ve watched him over the last five years and this year he’s really impressed me with how he’s gone about his business, changing speeds and playing with hitters more than anything. It’s been really impressive. I feel like he’s really learned how to use his stuff and he’s honing those skills he has right now.”

Akaminai, Casey McGehee and Kazuo Matsui each drove in runs for the Eagles, who maintained a 5 1/2-game lead at the top of the Pacific League standings.

Rasner relieved Tanaka in the ninth and retired the side for his 17th save of the year.

“It’s cool to be a part of,” Rasner said of the win streak. It’s real cool.”

The Lions, meanwhile, lost their fourth straight game.

Seibu starter Ryoma Nogami saw his five-game winning streak come to an end as he dropped his first decision since losing to the Yomiuri Giants on May 17. Nogami hadn’t lost to another Pacific League team since April 17.

Nogami (8-3) was charged with three runs on 10 hits in 7 1/3 innings. He struck out three, walked one and hit two batters. Nogami pitched well, but he’ll rue the fastball that lingered up and over the plate to Akaminai in the eighth.

Seibu’s Hideto Asamura finished 1-for-4 and drove in the Lions’ only run with an game-tying RBI single to left in the sixth.

“I felt like I needed to drive the runner home,” Asamura said.

The Lions missed a golden opportunity in the first when leadoff man Esteban German singled and Naoto Watanabe doubled to put runners on second and third to start the frame.

Tanaka retired Takumi Kuriyama on a weak grounder to first, Asamura went down looking at a 148-kph fastball and Shogo Akiyama grounded out to end the threat.

The Eagles loaded the bases with two away in the top of the second, and came away empty-handed when Nogami got Hiroaki Shimauchi to go down swinging on a 2-2 change-up.

Akaminai singled for Rakuten in the top of the fourth and scored from first on McGehee’s one-out RBI double.

Seibu’s Naoto Watanabe reached on a one-out single in the bottom of the sixth, and stole second while Kuriyama struck out at the plate. The steal proved to be critical, as the third baseman was able to come home on Asamura’s RBI single.

“I tried not to give up a run before we got on the board,” Tanaka said. “But I gave up a run right after we scored. “That’s something I have to reflect on.”

Akaminai homered on the second pitch he saw to lead off the eighth and give the Eagles a 2-1 advantage. Matsui tacked on an insurance run with a sacrifice fly later in the inning.

“I thought if we gave him (Tanaka) one more run, we were going to win,” Akaminai said.

Staff writer Kaz Nagatsuka contributed to this report.