Hello everybody! I can answer to the question as I am Japanese. It is district, cannot be someone's surname. In the begining of this post, some one said it is east sea, and Tokai means east sea, however there isn't any sea called East sea, at least major one. (I think the guy meant east chinese sea which is enormous one). Plus even if it is the sea, Tokai sounds very industrial district for me, (among Hamamatu (=Yamaha), Nissan (=..)
Hope there are more people to learn Japanese, from my point of view, it is really shame; although we are really good nationality (and makes great guitars) some people think it is part of china, at least people around me think so. Keep learning Japanese guys! If you get any chances that you become famous musician, recommend Japanese and Japanese guitars!