so, is there a way to make it so you can just collect a harem and never get the cheater mindset from anyone? or are you doomed to secret relationships forever? lol
With the modules from the AAU part of the character creator, I think there is a "polyamorous" module you can give a girl which makes it so she doesn't care about her lovers cheating; just give that to all girls and MAYBE it will work, I don't know how the AI would handle that module on max virtue characters, or with the dozen other modules that seem to conflict with it.
Without the module system? Still possible. Check out the Hgames wiki (just search "hgames artificial academy"). I know it has a section under gameplay tips about exactly this topic. I think what you have to do is get the girls to all be lovers with each other as well as your character; so you only need to be in a secret relationship until all your existing lovers become lovers with the new girl.
You can (probably) make this infinitely easier by turning on some of the cheat options in the in-game menu; I haven't tested them, but it seems you can change the "hate points" for both npc-npc and npc-pc actions to 0, which SHOULD make it so everyone can only improve their relationships with each other. You can make your PC actions 999% effective, which SHOULD mean that you can use the "try to get along with..." option to tell any girl to improve her relationship with another with guaranteed success.
There's only two issues I can see. First is that the "cheater" label may not just be connected to love/hate points, so girls might break up with/murder you even with the cheats if the catch you. Second is max virtue characters, who appropriately wont ever have more than one lover... unless you make them the PC and do it manually. If you download girls they might have some of the AAU modules which have similar effects as well, and I have no idea how the AI handles having multiple lovers in that case.
There's also a couple "corruption" modules which give you various ways to reduce a girl's virtue until she will take multiple lovers w/o direct control, that might make things easier. At any rate, it's complicated, but definitely possible, and makes for a fun and exciting end-goal for the game.
Imagine that, an illusion game with some kind of actual gameplay challenge to engage with instead of just robotically clicking dialogue options until everyone loves you.