In separate deals, the Mariners sent catcher David Banuelos to the Twins and the Angels sent outfielder Jacob Pearson to complete the transactions.
Teams interested in signing Ohtani are limited to the amount they have available in their international bonus pools. The Twins had $3.2 million in their international pool, but Ohtani narrowed the list of teams he was considering to seven finalists, and the Twins were not on the list.
Ohtani is listening to offers from the Mariners, who met with Ohtani on Tuesday, and the Angels, who met with him Monday, as well as the Chicago Cubs, Texas Rangers, Los Angeles Dodgers, San Francisco Giants and San Diego Padres.
The window for Ohtani to negotiate with big league clubs will expire at 11:59 p.m. ET on Dec. 22.
The 23-year-old Ohtani is 42-15 with a 2.52 ERA and a 1.08 WHIP in five seasons as a pitcher with the Hokkaido Nippon-Ham Fighters of Nippon Professional Baseball. He also has a .286/.358/.500 line with 48 homers and 166 RBIs over 403 games during that span.
Mariners general manager Jerry Dipoto was joined by Seattle's director of scouting Tom Allison, Pacific Rim liaison assistant Antony Suzuki and Japan-based scout Manny Noto to watch Ohtani play in Japan for multiple games in September.