Got all 12 grades, game just... stops?

Hello everyone!

I've read the guides about getting the different endings and rankings, and in my 1st playthrough I decided I'd try and get as many D's as I could, to get those "out of the way" so to speak.
In the end my rankings are like this:

L1, L2, L3 - D.
L4, L5, L6 - D because EXPIRED

K1, K2 - D.
K4 - C.
K3, K5, K6 - D because EXPIRED.

So that makes twelve, and there are no other missions I can do, but... I am at the character selection screen and only Data save and Data load are available as choices. I can click Louise or Kia, but all I see are the rankings, and then again Data save, Data load and return, so I'm stuck. There are no more missions I can select, so... how do I actually END the game?

You Should follow a walkthrough there's a a certain pattern of the missions you take and all of them have to be Grade A then you get two secret missions of Kia and Louise which are sort of two possible endings.

Here's a good walkthrough for you http://www.megaupload.com/?d=PYO4A4L4

ahh! wow that helps thank u kindly!!!

you are welcome ^^