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 .