The Brumbies' new Super Rugby era under coach Dan McKellar has survived a testing start in Tokyo against the Sunwolves.

Last year's Australian Conference winners had to wait until the early stages of the second half to edge away from their Japanese opponents before prevailing 32-25.

The victory never came easy and a penalty goal from the Sunwolves' Hayden Parker on full-time meant the Brumbies left Prince Chichibu Memorial Stadium without a vital bonus point.

The ACT team found themselves down at half-time, as the Sunwolves - who scored just three wins in their opening two Super Rugby campaigns - defied heavy underdog status to take a 19-15 lead.

McKellar's team stopped some serious attacking pressure from the Sunwolves in the last 10 minutes to ensure the first stop on a three-game away stretch was a success.

Brumbies co-captain Sam Carter said he was relieved to be on the winning side against the Sunwolves, who are led by former Highlanders coach Jamie Joseph.

The star lock expected them to surprise many teams in this year's competition.

"It was quite tough there for most of the game but we stuck to what we knew and got the result in the end," Carter said.

"I think it was a matter of keeping it simple, we just tried to push too many passes in the first half and the Sunwolves really capitalised on that.

"They are going to be a real threat and they were a great challenge for us today."

Full back Tom Banks, Tevita Kuridrani, Kyle Godwin and veteran hooker Josh Mann-Rea all crossed for tries, as did returning journeyman Lachlan McCaffrey in an industrious display off the bench.

Co-captain Christian Lealiifano had an impressive outing in his first Super Rugby start since 2016, putting the first points of the game on the board by slotting a penalty goal and playing all 80 minutes.

Towering Wallabies lock Rory Arnold saw some game time as he works his way back to full fitness from injury, coming on in the second half in place of twin brother Richie.

Nineteen-year-old Rob Valetini's Super Rugby debut ended early as a leg injury forced the promising backrower to the bench late in the first half.

While the extent of the injury is yet to be determined, Valetini was using crutches after the game and he appears unlikely to make Friday night's trip to Brisbane to face the under-pressure Queensland Reds.

"We're really devastated because he is a young kid on debut and he's been fantastic in the last couple of years with us so we really feel for the kid," Lealiifano told AAP.

Hosea Saumaki scored two tries for the Sunwolves, Timothy Lafaele crossed for one, while Parker was outstanding all game as he recovered from a heavy early knock.