By Rocky Swift

TOKYO (Reuters) -Japan erupted in cheers on Friday morning after national hero Shohei Ohtani blasted his way into Major League Baseball history as the first player to hit 50 home runs and steal 50 bases in a season.

"Ohtani-san" was the top trending topic on X in Japan, and chief government spokesman Yoshimasa Hayashi lauded the Los Angeles Dodgers star's "amazing achievement" in inaugurating baseball's 50-50 club with a six-hit, three-homer game.

"We would like to express heartfelt congratulations on achievement of this major record," Hayashi told reporters at a regular press conference. "We look forward to seeing more great things from Ohtani, who has already achieved so much and broken new ground."

The first batting and pitching dual threat in the majors since Babe Ruth, Ohtani has a been a focal point for Japanese national pride since his 2018 debut in the American League with the Los Angeles Angels, where he won two Most Valuable Player awards.

Every aspect of Ohtani's life has been a target for media attention, from his sudden marriage announcement this year and a gambling scandal with his ex-translator, to the name of his dog.

Ohtani-mania in Japan went into overdrive when he signed a record $700 million contract with the Dodgers at the end of last season and focused on batting following surgery on his pitching arm. Dodger blue replaced the Angels' red among best-selling jerseys in Tokyo, and every homer on the way to 50 was replayed on national news programs each night.

"Japan's record-making machine has done it again!" U.S. Ambassador to Japan Rahm Emanuel posted on X. "A true global ambassador of the game."

Takuya Tasso, governor of Ohtani's home prefecture of Iwate, likened the slugger's historic night to the "Big Bang."

"It's as if a singularity has opened, and a new universe is being created with his incredible performance," Tasso wrote.

With an imposing 6'4" (193 cm) frame and ability to crush 500-foot homers and throw 100 mph (161 kph) fastballs, Ohtani shattered expectations for ball players from Japan, said Robert Whiting, who has written about Japanese baseball for decades.

"Ohtani beats the Americans on their own terms," said Whiting, "He may arguably be the best ever, in MLB history, when you consider that he both hits and pitches at a star level."

"There are a lot of young Japanese, including Itsuki Takemoto of Wakayama now at University of Hawaii, who would like to follow in his footsteps, and may well do."