Suntory Sungoliath completed the league and cup double on Sunday as they beat Panasonic Wild Knights 15-10 in a pulsating All-Japan Championship final.

In front of a full house of 20,196 at Prince Chichibu Memorial Rugby Ground, five penalties from Kosei Ono saw Keisuke Sawaki's side finish the season unbeaten and take over Panasonic's mantle as Japan's No. 1 side.

"All season we have trained how to cope with unexpected situations and we showed that today," said Sawaki, whose side won the season-ending tournament for the seventh time.

"Panasonic defended really well and we couldn't attack as we wanted. But we showed great patience."

The defense of both sides was also praised by Panasonic coach Robbie Deans.

"It was a great final," he said. "A lot of rugby was played but there was just one try. You had two very proud defenses out there."

The first half was a tense affair with the boot dominating proceedings as both sides looked to play the game in their opponents' half.

Keita Inagaki had a standout game for the Wild Knights, making a couple of big turnovers, and Daniel Heenan made his presence felt with some big tackles, while Suntory lock Joe Wheeler stole a number of line-outs as both sides forced turnovers.

But with the tackling ferocious and the breakdowns extremely competitive, as one would imagine with the likes of George Smith and David Pocock playing, line breaks were few and far between.

Takaaki Nakazuru, who is set to sign for the Sunwolves next week, did have one good break down the flank for Suntory and Takuya Yamasawa showed great vision, pace and skill to gain 60 meters with a clever kick and chase.

But there were few outright try scoring opportunities, and it was no surprise that the half's only points came from the boot with Ono and Yamasawa exchanging penalties as the teams turned around level at 3-3.

The second half saw less kicking than the first, but tries were still hard to come by as both sides continued to throw everything into their tackles.

"You aren't going to get many tries against that tough Panasonic defense," Ono said. "We had to say patient and keep it simple."

Ono restored and then extended Suntory's lead with penalties in the 49th minute and 55th minutes before Heenan finally crossed the chalk after charging down a kick from the restart.

Yamasawa added the extras to give the Wild Knights a 10-9 lead. But it didn't last long as Panasonic's discipline let it down, allowing Ono to kick two more penalties.

"A couple of key moments didn't go our way and Suntory used all their cunning and experience," rued Deans.

The final 10 minutes saw Panasonic run everything as it looked to win the game at the death.

But Suntory's defense held firm, allowing Yutaka Nagare to lift the All-Japan cup two weeks after lifting the Top League trophy.

"Together with Panasonic we played a game of rugby to be proud of," the Suntory captain said.