This game is like a car wreck. You want to look away but just can't. I want to delete it and move on, but I keep coming back in hopes of figuring something else out. The walk through, in my opinion, is a disaster. It is 80 pages of constant searching because the characters are all over the place instead of being in one area.
If anyone has a better walk through that is more user friendly, I sure would appreciate it.
Also, can each character be developed individually or do you have to deal with multiples at any given time?
The game isn't linear, so the existing walkthrough is as good as it gets, you won't find another. It took some time, but I got used to using it, it takes only a couple of seconds to find the event you need. There's really no way to make a more convenient text walkthrough. The game is complex and so is the walkthrough, but it's one of the best games I've come across on this site and it's worth taking time to learn to play it.
As for the characters, you don't really have to deal with multiple girls at once, but often it's more convenient to pursue multiple girls because of time management. You can prioritize one girl, but it's useful to do other girls' events in between instead of just skipping days. There are also scenes, that require certain level of development with different girls. For example, if you go for Jessica, you must at least be friends with Jane, since she's your only option to level up massage skill. Alternative way to level up massage will be unlocked later during Jessica's quests, which can't be achieved without certain level of massage skill. There are also other examples, that require certain relationship with several different girls at a time, though mostly minor and optional, that can be ignored if you're not a completionist and don't mind missing an optional scene or even just extra render in a scene.