Two-time champions Japan beat Cuba 11-6 in their World Baseball Classic opener Tuesday, sparked by a five-run salvo in the fifth inning.
Nobuhiro Matsuda blasted a towering three-run homer to left field to put the Japanese in control of the Pool B clash in front of 54,000 at Tokyo Dome, pumping his fists and letting out a roar as he crossed the plate.
'Samurai' Japan were given a scare in the seventh when Alfredo Despaigne cleared the fence in right centre before Guillermo Aviles scored William Saavedra and Yurisbel Gracial to give Cuba a lifeline at 7-4.
Yoshitomo Tsutsugo looked to have settled nerves by smashing a two-run homer in the bottom of the inning, only for Gracial to drive in Frederich Cepeda and Despaigne in the top of the eighth to keep things interesting.
But a Matsuda single and a sacrifice fly from Seiji Kobayashi added late runs to seal victory for Japan, chasing a third title after scooping the first two editions of the World Baseball Classic in 2006 and 2009.
Starting pitcher Ayumu Ishikawa surrendered one run on two hits in four innings, with one strikeout and one walk.
"There was a strange sense of nervousness at the start," Japan manager Hiroki Kokubo told reporters.
"I knew the players would feel nerves but it was important to stay composed. Today's already finished -- we're already thinking of tomorrow and going on to win all of our games."
The Japanese take on Australia on Wednesday while Cuba will look to bounce back against China as both teams look to underline their title credentials.
Japan's hopes of completing a hat-trick of tournament victories in 2013 were undermined by the absence of players such as Ichiro Suzuki and Yu Darvish, while they almost pulled out of the event after a row over sponsorship revenue.
The Dominican Republic went on to lift the trophy.
Baseball's birthplace, the United States, has never won the Classic with Major League clubs refusing to release players, giving rise to questions over the tournament's future.
This year's 16-team competition concludes with a final at Dodger Stadium, Los Angeles, on March 22.