Japan certainly has some unique foods. One famous/notorious example, which even the most adventurous eater might think twice about, is Ikizukuri:
ikezukuri (活け造り), (roughly translated as "prepared alive") is the preparing of sashimi (raw fish) from live seafood. In this Japanese culinary technique, the most popular sea animal used is fish, but octopus, shrimp, and lobster may also be used.
The practice is controversial owing to concerns about the animal's suffering, as it is still alive when served.
...The restaurant may have one or several tanks of live sea animals for a customer to choose from... Ikizukuri fish may be prepared with only three knife cuts by the chef. They are usually presented with the head still whole so that customers are able to see the continuing gill movements.
Similar traditions exist in China and Korea (film fans might remember the live octopus eating scene from the original Oldboy) but there are some major differences described in this blog:
the Chinese have their own way of Ikizukuri, deep-frying the fish and keeping them alive till they are eaten, known as Yin Yang fish
In Korea, this practice is less cruel. Sannakji which are small octopuses cut into little pieces and usually lightly seasoned with sesame oil and sesame. While they are already dead, their nerves and suckers are still active, causing them to squirm and stick to the insides of your mouth. I’ve had the opportunity to try this, and let’s just say there wouldn’t be a second time. One [has] to be careful to chew them carefully as several cases of choking have been reported as the suckers stick to your throat when swallowing
Curiously, the foodstuff of Japan that presents the biggest danger and causes (I believe) the most deaths is actually one of the most seemingly ordinary: extremely sticky mochi rice cakes, which are easy to choke on and difficult to dislodge, and cause several deaths every year, usually around New Year celebrations.