KOYA, Japan — Ryusho Soeda, 66, has taken on a job for which his career as a Buddhist priest never prepared him: forensic accounting.

Mr. Soeda’s temple is the 1,200-year-old Koyasan temple, deep in the mountains of western Japan and long prized as a haven for quiet contemplation. But in recent months, monks at the site have been debating a very worldly question: How did a complex bet on the yen go so horribly wrong?

Mr. Soeda, who was picked to head Koyasan in June after his predecessor had been forced out, has promised a full accounting of the temple’s losses, which at one point last year threatened to wipe out half of its endowment.

“My duty is to find out exactly what has happened and to publish it,” Mr. Soeda said. “Just like Greece published its window-dressing only after they had a new government, the truth will not come to the light unless you change the power.”