I will try explain it.
1) Pick Akira
2) Stage 2-1 shoot all girls!! only the girl hiding behind the pole is not needed (after the 3 girls on the roof). Before entering the swimmingpool Mako will be on the right of the other 3 girls sitting on the bench (gym outfit). I took me a couple of tries to get this one. She showed up when I did everyting as described.
3) Stage 4-2 their will be this girl that runs (look at pictures at the links) between the lockers. I went in tokidoki on her or any other girls to make sure I had her. If you miss her the first time you will turn right and go tokidoki on an other girl. This will do the trick. If you do miss her you will follow her to the right and have to try again. (just let killed and you will start on stage 4-2 again).
If you managed to kill her you will not go right but instead look left. 3 girls are standing there. Kill them FAST!! I do not recommend using tokidoki, might kill Mako thats hiding. If you kill those 3 girls fast enough Mako will jump out the door on your left (swimsuit). Be quick or you will miss her.
4) Last time is on stage 5-1, she's just standing there with 3 other girls. But can hard to see since the all start screaming love words at you. She's second from the left.