I'm trying to figure out how to get the foursome vs the threesome. My "Forbidden One" playthrough didn't get it; but the harem route I started today did get it.
To get the foursome, the variable "adaknows" needs to be set. It's set at the start of day 7 (and a couple other places) if "ellydicktouch" is not zero. "ellydicktouch" is set at the start of day 4. If "ellyc" >= 50 it will jump to ellylove2, and in a little bit Elly will fondle the MC while he's sleeping, then "ellydicktouch" will be set.
"ellyc" is only set to 50 or 100 if the MC does things to pursue Elly - asks if he can join her in the shower, peep in the shower, buys clothes for her at the mall, etc.
So, to get the foursome you have to start off pursuing Elly.
@Luxee is the foursome only supposed to happen with the Harem walkthrough, or also with the Forbidden One walkthrough?