The dev is right, you really don't need a walkthrough. But I will hit upon the main points that might not be too obvious.
1. Raise your massage skill through watching videos. Hits 10 as a max, I believe.
2. Get a job and work often enough to get raises/promotions. This will impress Karen.
3. Try going to Karen's work once, get rejected. Eventually she will ask you to bring her something, and will be fine if you stop by later.
4. Give girls money every chance you get. Never deny them.
That is really it. Basically, by choosing all positive score choices and doing the above, you are golden. Major events occur at 2300hrs when you choose Sleep. For the NTR side, it is even easier: always choose negative options, and eventually Devon begins to swoop in.
Simple.