- Yu Tamura scored 18 points on eight of 10 kicking to pace Japan, who added a bonus point through Matsushima's try long after full-time to take control of their own destiny
- Samoa threw down the challenge before the game with their fearsome "siva tau" war dance on a cool night in Toyota
- Then almost five minutes after the final gong, Matsushima darted over for his fourth try of the tournament to bring Japan a precious bonus point
Hosts Japan conjured the samurai spirit to smash Samoa 38-19 on Saturday and take a giant step towards a historic quarter-final spot at the Rugby World Cup.
Tries by Samoan-born Timothy Lafaele, Kazuki Himeno, Kenki Fukuoka and Kotaro Matsushima helped make it three wins out of three for the Brave Blossoms, who returned to the top of Pool A.
Yu Tamura scored 18 points on eight of 10 kicking to pace Japan, who added a bonus point through Matsushima's try long after full-time to take control of their own destiny.
After beating Russia 30-10 and then stunning Ireland 19-12 to top Pool A, Japan face Scotland next week in the biggest game in their history.
"I'm really proud of our team, especially at the end there - it was a never-say-die attitude," said Japan coach Jamie Joseph.
"At the end of the day the belief in our team has grown and I guess we will need it going into next week."
Samoa threw down the challenge before the game with their fearsome "siva tau" war dance on a cool night in Toyota.
But in the heartland of the ancient samurai warriors, it was Japan who showed the greater hunger and fight as the Pacific islanders made an early exit.
Tamura and Henry Taefu traded a handful of penalties in the early skirmishes before Lafaele scored the game's first try just before the half-hour mark after swarming Japanese pressure.
With Samoa's TJ Ioane in the sin bin for a late hit on local boy Tamura, Lafaele spotted a gap and crashed over to the joy of 45,000 fans at the Toyota stadium.
Samoa full-back Tim Nanai-Williams, cousin of All Blacks superstar Sonny Bill, went off with a head injury just before half-time after being smashed by James Moore - his failure to re-emerge a big miss.
Leading 16-9 at the break, Taefu's boot brought Samoa to within four points before Tamura slotted a penalty of his own and Himeno bulldozed over after 54 minutes.
The crowd's excitement reached fever pitch as Japan's maul rolled on from a lineout and Himeno completed the job.
Samoa had won 11 of the 15 Tests played between the sides but it has been seven years since they last beat Japan.
Himeno's try knocked the stuffing out of the Pacific islanders, who reached the World Cup quarter-finals in 1991 and 1995 but have been cannon fodder for the bigger teams in recent tournaments.
Taefu scored and converted a try that gave Samoa brief hope before Fukuoka added a late third try for Japan.
Then almost five minutes after the final gong, Matsushima darted over for his fourth try of the tournament to bring Japan a precious bonus point and give the scoreline a slightly flattering complexion.
Samoa crashed out of the tournament after their opening 34-9 win over Russia was followed by a 34-0 drubbing by Scotland in their next game.