the middle left scene unlocks with 3 hearts and let it go. the middle right scene is with 1 heart. the number of hearts is obtained a little randomly I would say, I went from 1 heart to 3 or from 2 to 4
If you were talking about the 2 endings (submissive man and love), you have to unlock the 3rd fight scene. for submissive man, beat 1x at the beginning by making her cum, then she must jump you with the 4 hearts, finally lose for the 3rd round. the dialogues I don't remember very well how I succeeded :/ for love, no sex, discussion only. After beating 1x, take 1st choice, after beating second time, take 2nd choice. beat at the end. I admit that at the dialogue level I paid little attention but there should not be 2 dialogues with 2 choices each. Just try every possibility and you unlock. Otherwise, the rest of my approach is normaly ok