Japan rugby boss Jamie Joseph said he wanted his players to "feel the pressure", after warming up for the British and Irish Lions with a win over a select team on Saturday.
Japan returned to action for the first time since their historic 2019 World Cup exploits, coming from behind to beat the Sunwolves 32-17 in Shizuoka.
They travel to Edinburgh to face the Lions on 26 June, before taking on Ireland in Dublin on 3 July.
Joseph said he knew the game "was going to be a bit scrappy" after more than a year and a half since Japan last played in a World Cup quarter-final loss to South Africa on home soil.
But he welcomed the sparring practice against a team playing under the Sunwolves name - last used by Japan's defunct Super Rugby franchise - and hailed his players after coming back from a sticky start.
"I want the players to feel the pressure, because that's exactly what we're going to get every time we play a Tier 1 team," he said.
"Today for the first 50-odd minutes, the Sunwolves put us under a lot of pressure, and we struggled at times. But we were able to overcome that, and that's a really pleasing sign."
Japan started with 13 World Cup heroes in their line-up, but quickly came under pressure and trailed 14-3 at half-time.
They came roaring back with four tries in the second half - including two from substitute Kosuke Horikoshi - and Joseph said the match had helped blow away a few cobwebs.
"It's given us something to think about with regards to who's going to get selected for the Lions game," he said.
"I felt it was always going to be that type of match, which was exactly what we needed going into a really tough campaign in the next two weeks."
Ryoto Nakamura and Tevita Tatafu also scored tries for Japan.
They were without Clermont winger Kotaro Matsushima and Otago Highlanders loose forward Kazuki Himeno, who will join up with the squad in Europe.