Hideki Ajima spent months preparing for this year's “Sasuke,” adjusting his gym routine to focus on specific muscles that would help him conquer the famed obstacle course. The biggest challenge he faced, however, was a mental one.

“It was the wait before,” the 19-year-old performer currently part of talent agency Johnny & Associates Johnny's Jr. group Shonen Ninja tells The Japan Times regarding his debut performance on the show. “While I was waiting for my turn (to run the course), I became hyper aware of just what my number was. Watching as other people fell and faced challenges made me think over how I had trained, what I had done and maybe not done.”

Anyone, even a J-pop performer, would be intimidated by the physical challenges laid out by “Sasuke,” which airs its end-of-year extravaganza on Dec. 28 at 6 p.m. on TBS. Since debuting in 1997, the series has presented celebrities and regular folks alike with challenging courses testing their athletic abilities, from jumps across pits to having to cross a balance beam through what looks like rotating punching bags — the “Fishbone.”