If the manga boom continues much longer, we may soon have almost as many genres represented here in the States as there are in Japan.  Latest case in point, Viz LLC.'s recent announcement of the April release of the first volume of the Prince of Tennis manga.  Written by Konomi Takeshi, The Prince of Tennis first appeared in Shonen Jump in 1999 and has become one of the most popular sports mangas in Asia.  It is the story of Echizen Ryoma, a 12-year-old, who returns to Japan from the U.S. where he was four-time national junior champion.  The young sports prodigy joins one of Tokyo's top tennis club and he and his teammates battle their way to the national championship.  The manga series was so popular in Japan that it spawned a long-running anime series from Production I.G.