A silly question about game progression?

[Confused.]

[Sorry that I haven't registered, I'm kind of a forum lurker now, in the past I've registered on so many and then just left, I feel bad for wasting the space for a profile. >.o I really don't know that I'll return after having my confusion resolved & thanking, haha.]

First, how I came about playing;
So, I was talking to a friend on the phone, he asked me about running, me, of course, replying with something eventually leading to my heart problem.
"What is it?" "Wolff-Parkinson White syndrome.." He replied with, "Oh, you have arrhythmia?" I replied yes, figuring it was close enough. Then, he started talking about some 'Visual Novel" I figured, just a slideshow of images with text, or a picture book, nothing interactive. [I'm surprised, I've grown to love VRGs, you'd think something like that would have come to mind.] He tells me about it further, and it seemed interesting.
Later, he sends me a link to the download of the game, the site telling me nothing about it, and it looking like anime, and the word 'hentai' mentioned, I just kind of ignored it. [Not too big of an anime fan.. Ergo Proxy, Elfen Lied, & Cowboy Bebop are about where I stop, and even those irk me from time to time. And, want to avoid hentai like a plague. Porn = not my thing. Animated porn = much, much less so. haha.]
Later he starts sending me scenes from it on youtube, immediately seeing the imagery and emotion, I was interested. Later, sending me a gameplay video, I realized it was what he had sent me the download for before, and I dug it up.

Now, on to my question;
I just got an ending with Emi, obviously, I can see where you'd get the multiple endings there, but, after the credits started rolling, I had no idea what to do. [And, in playing, didn't see how I could end up with anyone else? I figured maybe it's a linear path, each girl in a row. But, now, browsing here, I see you can get any one first..]
I skipped the credits, ended back at the main menu, figured, okay, I load my file, and it's a fresh start with my progress saved, that must be how it works.
No, it took me back to my only save, last night before I went to bed..
Should I skip through and finish the credits for further options? Should I create an additional file? I know the chapters I went through are saved considering their images on the main menu, but, I still kind of thought it would progress rather than cause me to start over multiple times, or something to that effect. >.o
If it is done by separate saves, if I go through the story with the same girl again [Required, as, since I saw it as, well, a normal game where, you just progress to the end without having to start over unless you want a different ending] Will it register that I've gotten them all? Or, is that even important? I hear people talking about completion, but I haven't stumbled upon how to see that, either.
It seems it's come quite obviously to everyone else, so, I feel a bit stupid. I'm sorry. haha.
I would've asked him, but he just went to bed, and, if I have a chance of not having to wait to play, I'll take it.
Playing around with it, still, I may end up answering my own question considering how long it may take for a reply, regardless, any help is greatly appreciated, even if no longer needed. c:
Thank you!

[Fronzel]

I don't even know what you're talking about.

To get a different ending, you need to meet certain conditions based on your choices. If you have a saved game at a critical choice, you can take the other option and see the other ending.

To get on a different girl's route, you need to make different choices in Act 1. You must have noticed that certain choices pleased or displeased certain girls, or just resulted in you spending more time with them. You got on Emi's path partly because you had Hisao almost die on the running track and Emi started fussing over him to make amends.

Completion of scenes is automatically saved independent of saved games. As soon as you enter a scene, it's unlocked in the library.

[alabaster]

You ended up with Emi because it's probably the easiest route to just sort of accidentally stumble into. All the choices you make in Act I affect which girl's path you get into beginning with Act II, so basically you just need to go back and make different decisions, ones you think will help you gain the favor of whomever you're interested in. If that fails, look at the flowchart, but that takes the fun out of it.

[Confused.]

Ah, I've realized how to get other characters, and why I got her. Sorry, I kind of venture off on rants. >.o
I'm going to have to start over with her, anyway, as, I saved about half way through, but, that's no bother.

I was just confused as to whether it progressed, or, I had to start a new file for each character and if I'd have to skip through everything again in order to be able to do so.
I suppose that's kind of been summed up though by Fronzel's post though, I believe. Just a file for each girl, no need for a new file for each ending, I just have to save it properly so I can backtrack.

Again, I apologize. Just one of those "D'oh!" moments...
Thank you both!