Try basashi - horsemeat
Kumamoto is known for horsemeat and it is a regional specialty they are quite proud of. It is served raw on a plate, with a side of soy sauce and ginger paste, sometimes garlic paste. Shaved white onion adds to the flavor. The meat is cut in a certain fashion to avoid the chewiness of typical raw meat.
When you eat basashi, you will probably find it indistinguishable from raw beef. It should be served at room temperature and can be purchased at almost any grocery store though there are specialty stores. Look for horsehead placards outside to spot them.