I just saw a lot of mention of blue heart in the thread, I think those are for 4th heart and up. I'm just having trouble even getting the third heart on day one, I already maxed out all the shop
If you try and spend a lot of time, then on the first day you can get all the endings.
Firstly, you should not talk to the princess too often, ideally in the first minutes you need to quickly get a cloud with a green heart (Calm down / gentleman) and with a blush (praise). Then proceed to caresses and wait until the hearts stop appearing. As soon as the clouds with hearts stop appearing, repeat a several of dialogues again. From time to time you need to ask about the feelings of the princess. But undressing, in principle, is not required at all. But if the princess is not completely undressed, suggestions will appear when choosing dialogues.
There is the easiest way to get the 4th heart on the first day, but with the rejection of masochistic endings for 5 hearts. To do this, we get the 2nd heart and show the collar to the princess, quickly promise to throw it away. You immediately have 4 hearts, but there will no longer be an opportunity to get the 5th heart.
And by the way, to get the 5th heart, it is not necessary to abuse the princess to the very blue tint. enough to get 4 full hearts, bring to orgasm. With the onset of orgasm, quickly show the collar, put it on and start stroking the head.