Finished the Volleyball Story!

Once I figured out the trick, it was just 3 stars all the way. After getting Zero Mint to level 15, I also got Shinku Iroiro to level 15. When serving, if you watch the opponent's position and just stand to the sides, they move to the center of the court, and if you hit a strong serve straight between the two opponents, they can barely receive it. As long as you get the serve, the game is pretty much over.. The difficulty doesn't seem to ramp up too much even when you reach Pro. So if the opponent serves first, I receive, spike what my partner sets up, win, and then if I get the serve, I score 6 points right away and the match ends lol