I haven't looked at a Walkthrough since my very first playthrough so I may be talking out of my ass here...
Something people using a walkthrough need to understand here, it is not a true walkthrough in the sense that you follow it to the letter and you get everything. It is broken down by character and some events for a character require you to have done events with some other character first.
i.e. To get the Massage Oil and proceed with Amy you need to :
- Have taken Veronica's Panties away from her
- Have given Claire a massage without the oil (Which tells you it would be better if you had some)
If you were just following Amy in the WT then you might not know those two things were required.
So it isn't really a walkthrough in the same sense as is usual, You do step one which leads to step two and then three and eventually at the end you have seen everything.
It is more of a hint system to tell you what can be done and when you can do it provided you have done all the things required to get them. Trying to do just one character fully and ignoring the others simply won't work.
This is why the HINT system built into the game is your best option to getting past a accomplishment and if the hint isn't telling you enough you can then look at the WT and see what the hint might be suggesting you try.