Oyu picked up the injury during training ahead of this weekend's sixth round of the season, and was seen at the circuit on Friday with bandages covering his right arm and shoulder (pictured top).
As a result, he will be unable to take up his seat at the TGM squad this weekend.
"It happened on Monday," Oyu told Motorsport.com's Japanese edition. "Initially, I got in the car and it felt like I might be able to drive. It hurts, but if it was purely up to me, I would have chosen to race.
"But those around me said I shouldn't force things. I am pretty certain I can race in the Fuji SUPER GT race [in early August]. That said, it depends how well it heals, and if the person deciding says 'no', then there's nothing I can do."
Oyu's injury is the latest in a long line of misfortunes this season for the 24-year-old, who joined the fledgling TGM team this year from Nakajima Racing.
He has failed to finish the last three races in a row, dropping out of last month's Sugo race due to a damaged floor, and hasn't finished inside the top 10 since the opening race of the year at Fuji, where he finished seventh.
However, the bonus points he has earned in qualifying, including two pole positions, have kept him joint-eighth in the standings.
Otsu meanwhile is making his second appearance of the season as reserve driver for the Honda camp, after he drove for Team Mugen in place of an unwell Tomoki Nojiri at Autopolis in May.
A qualifying crash on that weekend restricted Otsu to a 14th-place finish, but a berth at TGM this weekend will give him another chance to show Honda he deserves a reprieve after losing his regular seat at Dandelion Racing.
Otsu was in action in last month's in-season test at Fuji, where he drove for B-Max Racing in a move designed to help the team escape its current poor form.
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