Why can't it find the record of my e-mail address?

I’ve run into a little bit of a problem. I clicked to purchase a game (specifically, Samurai of Hyuga if it matters) and it asks me to enter the e-mail address I use on this site. I entered the one I use on the forum, which I assumed was what it asked for. But it displays, in red letters, that it can’t find the record of my e-mail. Am I doing something wrong or does the problem lie elsewhere?

Are you trying to purchase from the choice of games website? If so, it should let you create a new account when purchasing the game.