The 'Ikale Tahi's four match winning run against the Brave Blossoms came to a thuddering halt in Toulouse as the Japanese ran in five unanswered tries.
Toutai Kefu said they missed too many tackles in a poor performance.
"I think our attitude probably wasn't right to start with," he said.
"We lacked a little bit of urgency around the ruck and if you don't have that it's 100 percent attitude and just mental aptitude, to be hungry enough to win the ball.
"So I think from our point of view that's the first thing we need to fix."
Despite being disappointed with the performance of his team, Kefu said it was pleasing to blood some new faces in the test arena.
Former Chiefs number eight Maama Vaipulu and Counties Manakau flanker Fotu Lokotui made their test debut in the back row, having also started the 27-24 defeat by the Barbarians a week earlier.
Meanwhile Jethro Felemi, Onehunga Havili, Penikolo Latu, Sione Lolohea, George Taina, Shinnosuke Tu'umoto'oa and Sione Vailanu earned their first test caps from the bench.
"We just wanted to see what they were like. We thought that this was the time to experiment and to have a look at those players," said Kefu.
"We found some really really good players - ones that we already knew like Maamu Vaipulu, who's a high-class player, but the little openside: he certainly looks to be a player of the future for us, young Fotu Lokotui, so we've unearthed some gems."
The 'Ikale Tahi round off their November tour in Bucharest this weekend, against a Romanian team that defeated Manu Samoa 17-13.