The Borussia MG attacker saw his stock rise after scoring three goals in the Olympics and could find himself following in the footsteps of former Japan captain Shunsuke Nakamura
The 22-year-old spent most of last season on the outside looking in at Borussia Monchengladbach, making just three appearances. But he emerged rapidly in the 2012 London Olympics, scoring three goals - including the shocking game-winner against Spain - on the way to Japan's unexpected fourth-place finish.
"We've received an offer from Celtic and are in negotiatons," a source close to Otsu told Sponichi. "Once we settle on the terms the transfer should go through."
The former Kashiwa Reysol man told his club's website earlier this month that he expected to be loaned for the season.
A move to Glasgow would draw inevitable comparisons between Otsu and Japanese legend Shunsuke Nakamura, who scored 33 goals in 164 appearances for the Hoops. Winger Koki Mizuno, once a team-mate of Otsu's at Reysol, also spent two and a half years at the club, making just 11 appearances.
The loan would also allow the youngster a chance to participate in the Champions League group stage, after Monchengladbach's chances of progressing in the tournament were severely threatened by a 3-1 loss to Dynamo Kiev in the play-off stage.