Ippei Mizuhara is behind bars — Shohei Ohtani‘s former right-hand man and interpreter has surrendered to federal authorities to start his 57-month prison sentence.

A spokesperson for the Federal Bureau of Prisons confirmed to TMZ Sports that 40-year-old Mizuhara reported to the Federal Correctional Institution Allenwood Low facility in Pennsylvania on Monday … hours before the Japanese superstar is slated to make his first pitching start for the Los Angeles Dodgers.

Mizuhara was sentenced to 57 months in prison this past February for stealing more than $16 million from Ohtani … and was initially ordered to surrender in March, but the date was pushed back at his attorney’s request.

The Dodgers fired Mizuhara in March 2024 after Ohtani’s attorneys claimed he engaged in a “massive theft” of the World Series champ’s bank accounts. He was accused of taking funds from Ohtani to place bets and pay debts to an illegal bookmaker.

“He took advantage of his position of trust to take advantage of Mr. Ohtani and fuel a dangerous gambling habit,” United States Attorney Martin Estrada said. “My office is committed to vindicating victims throughout our community and ensuring that wrongdoers face justice.”

Mizuhara was facing up to 33 years in prison … but ultimately reached an agreement, pleading guilty to bank fraud and filing a false tax return.

Ohtani addressed the matter at the time … saying, “I’m very saddened and shocked that someone who I trusted has done this.”

The 30-year-old has denied having any knowledge of Ippei’s gambling activity or the debt he incurred from it — which reached $40 million in the negative.