When Tozan is chasing the tourist shop owner, he runs forcefully into a closed door, causing the entire wall to visibly shake, revealing that the interior of the shop is a film set.
Magnum acts like he doesn't know what seppuku is BUT in an earlier story, entitled the taking of Dick McWilliams, he mentions it to Dick McWilliams' father in law with regards to Dick McWilliams' wife committing Seppuku.
At minute 28, Higgins rings the bell and Magnum with his sake hangover grabs his head but does not cover his ears, which anyone would naturally do.