Wataru is a young man who moves into an apartment next to Tomoka and Fumie Fusono, two voluptuous sisters who used to know him when he was a shy child. Now Wataru is all grown up, and the Fusono sisters are ready to take full advantage of that fact.

Due to an accident, Wataru has lost his memories. Now he is in America with Rena and she has promised his parents that she would take care of him until he recovers. Well, she isn't the only one that wants to help him out! Two boobalicious babes from Japan have followed Wataru to America and they too vowed to find a way to have his memory recovered. The method: Making sure he remembers how much of a boob-lover he once was by using their boobs as tools!

The Big Tit Grandprix is just around the corner and the girls are pumped! Through this competition, the girls have decided that whoever wins will win both the cash prize and Wataru's heart. Which of these three girls will be the ultimate winner? Will any of them be a winner? There's only one way to tell, watch the Big Tit Grandprix! (Man...Wataru, you sure are one lucky dog!)