It took me about 4 playthroughs to realize the trick. You go to the last option when talking to girls and choose the top option for +1 or the second, bottom option for -1. You have to check the sheet of their opinion of you often to make sure you have not gone past a scene; each scene is indicated by a golden lock and is required to unlock the next, so just pumping either Hate or Love won't work. This is also way easier and faster than going through the minigames.
Along with that, you will see a color coordinated Half-Heart symbol next to a few of them which indicates the scene contains both of them. For instance, the fox demon and pink-haired Succubus both have a pink heart half at Hate. So, after viewing all Hate scenes for both of them, assuming they are both at 10 Hate, there will be a special scene involving the 2 of them.
Unfortunately, I didn't get all the 10-Hate scenes; I had accidentally purchased a treat for them, so 3 of them were at -9 instead of -10 and they refused to let me play with them or anything. So I get to go through again just to get 3 Hate scenes at the end
I also recommend, for anyone playing the game, to go to the Blue Box in the classroom as soon as you can (Only starts to shine on the 2nd day) and just mash Z through it. This will set your game to Easy (Get 40 health/energy recovered while resting instead of 20) and will allow you to skip the boring walking to your bed. It will literally put you facing your bed so you just hit z, then like 2 spaces from the door as soon as you wake up, and it also skips the morning introductions. It just generally makes the game go a lot faster.