The Ireland U20s breathed a big sigh of relief after Tommy O’Brien’s 76th-minute try steered them to a 39-33 win over Japan in a helter-skelter World Rugby U20 Championship play-off in Béziers.

Ireland’s only victory of the tournament in France saw them finish 11th overall and crucially secure a place for next season’s Irish team at the 2019 World Rugby U20 Championship in Argentina. Japan outscored them by five tries to four but are relegated to the World Rugby U20 Trophy for the second time in three seasons.

Two Munster players played their part in the win with centre Peter Sylvester among the try-scorers and back-row Jack Daly impressing throughout.

Tries from Jonny Stewart (4 minutes), Dan Sheehan (10) and Sylvester (33) established a 22-12 half-time lead for Ireland, who had a vital contribution from out-half Harry Byrne. Ross Byrne’s younger brother kicked 19 points, including four penalties in the second half, to finish with 42 points for the Championship.

Japan’s strongly-built danger man Siosaia Fifita kept them in touch with a quick-fire brace of tries nearing the hour mark, and fellow winger Halatoa Vailea’s 72nd-minute score, converted by Yuto Mori, made it a one-point game. However, Ireland showed impressive composure to work Tommy O’Brien over in the left corner and debutant Dylan Tierney forced a last-minute penalty at the breakdown to finally settle the issue.

Captain Caelan Doris, who made 17 of his 18 tackles and won two turnovers, said afterwards: “It was incredibly tough, it went right down to the last minute. That last defensive set we were all out on our feet. Thankfully Dylan came in with a jackal and won it for us. Incredibly tough game. We saw what Japan could bring, some really strong runners, and they came close against Wales and Georgia.

“So we knew it was going to be a tough battle and we’re delighted now to finish on a high. We had a very tough group, three really physical teams in France, South Africa and Georgia. Unfortunately we came up short but (I’m) delighted with the character the boys have shown to bounce back, and to make sure the lads next year are back in this competition is great.”

Injuries severely impacted head coach Noel McNamara’s selection before and during the tournament, so much so that five players were making their fifth starts in 19 days against the Baby Blossoms, including former skipper O’Brien who is booked in to have surgery on a shoulder injury this coming Tuesday.

Scrum half Stewart, making his 19th appearance for the Ireland U20s, ensured they put points on the board in a strong start. His half-back partner Byrne missed an initial penalty, but Japan were pushed back towards their try-line in seven phases and Stewart threw a dummy to snipe over from the back of a ruck and make it 7-0.

Number 10 Byrne made a terrific break from his own in the build-up to the opening try, while new cap Michael Lowry was also looking lively from full-back. Try number two was all about the forwards and a clever lineout move, hooker Sheehan throwing in five metres out to Jack Dunne, Cormac Daly combining with Doris who switched back to the short side where he sent Sheehan powering over in the corner.

Trailing 12-0, Japan regrouped and one of their leading lights throughout the tournament, Vailea, crossed for a much-needed converted try on the quarter hour mark. They varied their attack, threatening from a cross-field kick which Lowry did really well to gather. However, a penalty advantage allowed them to set up a well-executed maul and tighthead Tsukayama touched down to bring them level.

It was further evidence of Ireland’s frustrating ability to cough up points after scoring themselves, but they diligently wrestled back control of the game and the scoreboard in the lead up to the interval. Number 8 Doris tore through the Japanese defence, with Byrne running a very good support line before splitting the posts with a 29th minute penalty for offside.

McNamara’s charges were quickly back within scoring range thanks to the efforts of James Hume and Doris again, and UCC centre Sylvester managed to muscle over for a try following some sustained pressure on the Japanese line. Byrne successfully negotiated the tricky conversion into the wind, giving Ireland a 10-point buffer at the break.

Doris and his team-mates appeared to tighten their grip on the game in the early stages of the second period. The reliable Byrne knocked over successive penalties after 43, 47 and 49 minutes to open up a 31-12 advantage. But it was his missed tackle in midfield when allowed the Tongan-born Fifita to spark Japan back into life with a well-taken 55th-minute try, converted by Mori.

The distribution of Mori and influential replacement scrum half Shinobu Fujiwara was bringing Fifita and the Baby Blossoms’ big carriers more and more into the game. The Japanese pack went through the phases following a penalty and a lineout deep in the Irish 22, and Fifita again proved unstoppable as he crossed to suddenly close the gap to 31-26.

Byrne punished a collapsed scrum to send over a 63rd-minute penalty and steady Ireland at 34-26, but Japan had more in reserve with their forwards continuing to work hard and both Fifita and Vailea proving tough to stop. They tried to stretch Ireland and it did the job as Vailea was quick off the mark to finish an opportunity with eight minutes remaining.

Accidental offside gave Ireland the platform of a scrum in the Japanese 22 and nice hands from Byrne and centre Sean O’Brien set up Tommy O’Brien to evade the clutches of Vailea and crash over in the corner for the ninth and final try of this gripping contest.

Byrne was unable to convert the winger’s expertly-finished score, but Japan’s last-gasp attempts to manufacture a response – taking Ireland through 19 phases – were thwarted by replacement hooker Tierney who was unmovable as he latched onto a breakdown ball to win the clinching penalty.