Ireland head coach Andy Farrell insisted he savours any win over Japan nowadays given the progress the Brave Blossoms have made on the international stage in recent years.

Farrell's side were lacklustre in the first half at the Aviva Stadium in front of 3,000 spectators, the first time fans were back at the venue since February last year, before recording a 39-31 victory on Saturday afternoon.

Chris Farrell, Stuart McCloskey, Finlay Bealham, Josh Van Der Flier and Jacob Stockdale touched down while Joey Carbery, making his first Ireland appearance since the 2019 World Cup quarter-final loss to New Zealand, added the extras to four of those tries before two late penalties ultimately took the wind out of Japan's sails.

The lead changed hands several times in a pulsating summer Test, their first meeting since Japan memorably prevailed in the pool stages of the World Cup two years ago, but a more inexperienced Irish line-up won this time.

It was far from a polished performance but, with seven of their contingent on British and Irish Lions duty and regular captain Johnny Sexton, plus Keith Earls and Cian Healy, rested, Farrell was not taking the win for granted.

"There's no mixed bag from me, I'm delighted with the win," he said.

"It was always going to be a tough, old challenge for our group against what I believe to be a top-class international side, so any type of win at the Aviva was always going to be a great result for us.

"Every single game that we'll play against Japan from now on in will always be a close encounter."

Japan, ranked 10th in the world, six places below their conquerors this weekend, went ahead 24-19 in the second half but were ultimately left to reflect on a second-successive defeat.

They were also beaten by Warren Gatland's Lions 28-10 at Murrayfield last Saturday in their first outing since staging the World Cup, but Farrell has been impressed by what they have offered in these back-to-back contests.

"The brand of rugby is consistent, they are unbelievably dynamic and hard to stop on the break, they've got some very dynamic, powerful and skilful athletes across the board," Farrell said.

"They've not played that many games since the World Cup but if they had, I don't think 10th place in the world rankings is a true reflection of where they're at. They're a good few positions higher than that."

The win came at a cost for Farrell, who revealed Chris Farrell failed a head injury assessment after taking a blow shortly after the break, while Jordan Lamour is nursing a groin problem that forced his withdrawal after 31 minutes.

However, the former England defence coach thinks this was a worthwhile outing for a side in which eight of the starting XV had earned fewer than 20 caps.

"I suppose the most pleasing thing would have been it was never going to be perfect," Farrell added. "I thought we were a bit rusty, certainly in the first half that we compounded negative errors-on-errors.

"It made the game difficult for us. It looked like they had their legs about them more than what we did.

"Having said that, in the second half it certainly wasn't perfect again, but how we controlled the game with our set-piece and our field position, we continued to go after Japan which was the most pleasing thing.

"We managed to stay calm, we managed to stay in control, we managed to stay next-task focused and I think that got us through in the end."

Japan showed plenty of creativity and Michael Leitch, Timothy Lafaele, Siosaia Fifita and Naoto Saito went over, while Yu Tamura added 11 points with the boot, but head coach Jamie Joseph could not hide his disappointment at the result.

"I'm disappointed for the players, actually," he said. "I thought we played some great rugby at times and for a team that hasn't been together for nearly two years, it's a good sign for us.

"I'm very pleased for these two opportunities (against the Lions and Ireland) but also it's pretty gutting to have lost that Test match.

"We thought we prepared really well, we started the game really well. There were just key moments from my point of view that we lost."