Two-time defending Top League champion Suntory Sungoliath beat NTT Communications Shining Arcs 20-18 Friday at Prince Chichibu Memorial Rugby Ground to make it two straight wins to start the new season.

But for the second week running the champs were forced to dig very deep for the victory.

A week after they needed a penalty try long after the final hooter to beat Toyota Verblitz, Keisuke Sawaki's side was indebted to two of its young guns as 24-year-old Hikaru Tamura kicked 10 points and 22-year-old Yusuke Kajimura crossed twice before its defense held on to secure the points.

"It was a close game and we got the win, but we're not playing at the level of champions," said Suntory captain Yutaka Nagare. "We made too many 50-50 passes and knock-ons and couldn't create space to get the Suntory attack going."

In Friday's Red Conference game, Suntory was given the opportunity to play with a strong southerly wind at its backs in the first half.

But after a good start during which it scored 13 points, it was made to work hard as the Shining Arcs made the most of an injury to Australia international Sean McMahon to play itself back into the game.

Tamura kicked two penalty goals and a conversion and Kajimura chose the perfect angle from quick ruck ball to bisect the NTT midfield defense and cross the chalk in the 13th minute.

But with McMahon forced from the field in the 20th minute Suntory struggled, and NTT responded with Ryutaro Ueda rumbling over in the 31st minute and Jumpei Ogura kicking a penalty on the stroke of halftime as the teams turned around with just five points separating them.

"Suntory played beautifully in the first 15 minutes...but after that we were dominant for long periods," NTT coach Rob Penney said.

The second stanza, which saw the wind drop significantly, opened with a second penalty from Ogura.

But Suntory responded in the 57th minute through Kajimura as Suntory exploited the sin binning of NTT captain Shokei Kin following a period of sustained pressure from the Sungoliath forwards.

Another sin binning — this time to Suntory flanker Hendrik Tui — led to NTT's response in the 73rd minute as some good hands from Isaac Ross freed up Brackin Karauria-Henry for a try.

Ogura's conversion meant there were just two points between the sides as the game entered its final six minutes.

But Suntory held on, just, to send NTT to its second bonus-point loss of the season, having fallen 34-27 to the Kobe Kobelco Steelers in the teams' opener.

"It just came down to small moments that were defining. It was those little moments that we were not mature enough to get it right," rued Penney.

Suntory takes on Kobe next week, and Sawaki had a message for Nagare and the other senior players:

"We need our leaders to perform better."