The Japan Karate Association is a Shotokan Karate organization, so most of the people competing in such tournaments will be Shotokan Karate or something very similar. Those who aren't Shotokan, will study and perform Shotokan kata as well.
JKA tournaments use JKA rules, meaning that each competitor uses hand pads, mouth guards, groin shields, and for the ladies, chest protectors. They'll allow solid contact to the body, since anyone who competes should be in somewhat good condition, and will also allow light contact to the face. Excessive contact is penalized, unless it's the other guy's fault for not even defending.
Since you want something with no gear and full contact, a JKA tournament does not appear to be what you seek.
Instead, you're probably looking for a full contact knockdown tournament, something like the tournaments held by Kyokushin Karate organizations, such as World Oyama Karate, etc. Those tournaments use no padding (except groin shields and mouth guards), and allow full contact to the body (kicks to the head area allowed, but no punches to the head) and the upper legs. Here's a short list of tournaments that they support:
http://worldoyama.com/Events_Tournaments.html