Head coach Steve Tandy warned Wales must improve after a hard-fought 28-21 Nations Championship victory over Japan in Cardiff.

Wales recorded a bonus-point win as Josh Adams (2), Archie Griffin and Louis Rees-Zammit crossed, but they had to produce a desperate rearguard in the final moments to prevent Japan from an equalising score and a famous draw.

“It’s obviously good to start the campaign with a result, but I can’t run away from the performance when I talk about it,” Tandy said after only the fourth win of his 13-match reign.

“There are elements of the performance we definitely need to improve. I thought we’d be better than that in some elements.

“There was really good stuff from us, in terms of the line breaks and how we opened Japan up. But we weren’t ruthless enough and we didn’t finish those off, making them pay when it counted.”

Wales have now won two of their four Nations Championship games, but stay fifth in the northern hemisphere standings.

The next two weekends promise to present far sterner tests for Tandy’s side, with New Zealand and Australia due in Cardiff.

Tandy said: “Getting a hit out for the first time since the summer, it does get clunky.

“It helps to review after a bonus-point win. We’ll park that and enjoy it as we haven’t done that a lot.

“But the beauty of this group is the hunger to get better quicker. We’ll definitely have to do that for the next couple of games.

“There was some excitement in what we tried to do. Japan were effective close to the line.

“We managed the game really well outside of that. Defensively, we improved our robustness outside the 22.

“There’s bit in the game where there’s a lot to like. But in Test matches, you need to be ruthless and reward yourself when you’re on top.”

Japan remain fifth in the southern hemisphere table and are on course to meet Wales again on finals weekend at Allianz Stadium, Twickenham, at the end of the month.

The Brave Blossoms trailed 21-14 at the break after tries from Ben Gunter and Warner Dearns.

A converted score from Kenta Fukuda five minutes from time set up a grandstand finish that Wales managed to repel and cling on for the win.

Asked if it was a missed opportunity, Japan boss Eddie Jones said: “100 per cent. That could have been a historic win for us.

“But you’ve got to be good enough to take advantage of those mistakes. We weren’t quite good enough.

“I’m proud of my team. We had a particularly young team, some university students and one 10 playing his first Test. But they stuck at it.

“Once you get in the 22, if you don’t take points from that, I feel that’s the difference in the game now.

“We had three opportunities but we didn’t take chances and Wales did. Their points-per-entry was higher than ours.”