The Blues have melted in the Tokyo heat, going down 48-21 to an unfancied Sunwolves outfit in their final outings of the season in Japan.

In temperatures reaching 42 degrees in the Japanese capital, the Tana Umaga-coached Aucklanders could do nothing right in the second half and were duly flattened by their enthusiastic opponents.

With the heat clearly taking its toll, the Sunwolves ran in an unanswered 34 second-half points and celebrated like they had won the competition.

It's an extraordinary turnaround from the Japanese side, who had won just one 2017 game before Saturday and lost 94-7 just two weeks ago to the Lions.

The Blues finish another mediocre campaign on the worst possible note and farewell Charlie Faumuina and Steven Luatua sourly.

First-half tries to James Parsons, Gerard Cowley-Tuioti and Michael Collins handed the Blues a 21-14 halftime lead, considered slim against a struggling side like the Sunwolves.

But they contrived to embarrass themselves in the second stanza, conceding six tries to a Sunwolves side who never eased up.

It was the most tries they had scored in a game in their short Super Rugby existence.

"You can't take anything for granted in this competition," Blues coach Tana Umaga told the New Zealand Herald.

"They just wanted it more. That's all down to attitude. At the contact area they challenged us there and their defence was relentless.

"It made us make errors. We lacked a bit of focus on our game and when you haven't got the attitude right we get what we got today."

Ryohei Yamanaka capitalised on a Sam Nock error to score in the 54th minute, before a Jerome Kaino sin-binning unleashed panic in the Blues' ranks.

A Sunwolves penalty try followed - from a rolling maul, no less - before Kaito Shigeno, Timothy Lafaele and Yoshitaka Tokunaga rubbed salt in the Blues' wounds, as they face the long flight back to New Zealand.