(Reuters) -More misery was heaped onto Welsh rugby on Saturday as they lost the first of two tests in Japan for an 18th successive defeat, leaving them ruing missed chances to secure a first win in 18 months.

The international at the Mikuni World Stadium in Kitakyushu on Kyushu Island was a good opportunity for the beleaguered side to bring the unwanted streak to an end but Wales let a 12-point halftime lead slip as Japan rallied to snatch a 24-19 victory.

"It's very tough to take because we have worked hard. We take nothing away from Japan for the way they played and coming out on top but we had moments to win that game and put it to bed,” said Wales captain Dewi Lake.

"We just allowed Japan to play their game in the second half, and they're tough to stop when they're playing at speed,” he added.

Wales began brightly and scored three first half tries to go 19-7 up at the break but the heat and humidity caught up with them after the break, when they were on the back foot and put up a nervy showing.

Japan scored two unanswered tries in the second half and took the lead with nine minutes left, holding on for a win they celebrated vociferously.

"Obviously conditions are going to play a factor, but we're not blaming that, again we weren't clinical enough. The weather was a factor but we'll look at ourselves first," Lake added.

Interim coach Matt Sherratt, who took over during the Six Nations earlier this year when veteran coach Warren Gatland was replaced, also refused to blame the energy-sapping humidity.

"I would be making excuses if I said that,” he said. "If you look at the game, we took pretty much every chance we got bar one in their 22.

"We had a lead going into the first half so to lose the game at the end is very disappointing.

"We have a young group, we have not had a win for a while and those little scars can start to run deep.”

But Sherratt said next Saturday’s second test in Kobe would be another chance to win and record a first triumph since beating Georgia at the last World Cup in France.

"We have got to quickly use the hurt to fuel us for next week. The great thing about this tour is we get the opportunity to put it right."

(Writing by Mark Gleeson in Cape Town; Editing by Pritha Sarkar)