In Japan, Ryoma Echizen is famously known under his title as the Prince of Tennis, but no one really knows about the love life of the little prince. Somewhere in the states, a girl that's around the same age as Ryoma is known to be the Princess of Tennis. Ryoma made a promise in the past with the princess as a child before he left for Japan, but they haven't fulfilled that promise in over a year... Do they even remember the promise after such a long time? Will fate play in their favor? Or will something tear them apart?