Italy 47-22 Namibia.
Italy began their World Cup Pool B campaign with a bonus-point victory over Namibia in changing weather conditions in Osaka.
The Namibian part-timers took an early lead through Damian Stevens before the Azzurri drew level with a penalty try.
Italy then took control with tries from Tommaso Allan and Tito Tebaldi.
Edoardo Padovani, Carlo Canna, Jake Polledri, Matteo Minozzi scored after the break, while JC Greyling and Chad Plato scored consolations for Namibia.
Italy initially struggled in the pouring rain and had to wait until the 25th minute to take the lead, but as the sun emerged in the second half, the Six Nations side turned on the style as they overpowered their opponents, who at 23 are the lowest ranked side in the tournament.
Italy captain Sergio Parisse, 36, became only the third man to play in five World Cups, matching the totals of compatriot Mauro Bergamasco and Samoa’s Brian Lima, and his 141st international cap also drew him level with former Ireland and British Lions captain Brian O’Driscoll in second place on the all-time list.
“The important thing was to win and take the five points,” Parisse said.
“Big congratulations to Namibia as well because they never gave up. They kept playing to the end.”
The only negative for the Azzurri was when Tiziano Pasquiale was stretchered off before the break.
Play was briefly paused while the prop received medical attention for what appeared to be a neck injury.
Italy are next in action against Canada on Thursday, 26 September (08:45 BST), while Namibia face neighbours South Africa on Saturday, 28 September (10:45).
Defending champions New Zealand, who beat South Africa on Saturday, are the other team in the group.