Finished the game. It's pretty easy. Some might enjoy the puzzle mode too. In my opinion Lost Life is more frustrating than this one because unlike Lost Life you can really feel your progress here.
There are three endings. the Bad, the Good and the Slave ending.
You unlock the free mode and puzzle mode by getting the Good ending.
Bad and Slave Endings have two paths which just tell if you finish inside (breaking the curse and turning her back to human) or outside (remains a dog), on the 3rd Day.
The paths are pretty much the same except for the little menu splash art, which has dog ears for, you know, the Dog endings. You need to unlock both modes though for some options in the Free mode.
To get the Slave Ending, you have to start from Day 1 and read the dialogue until the part where she shows you the BDSM collar.
Once it hovers to the side you can click it and it will now appear as an option in the next H scenes. You can get all 4 hearts (the big heart counts as 1, so you have to get 3 small hearts) in Day 1. Just keep telling her compliments, concern and calming dialogue (You are the princess, Do you like it, Dont worry bla bla bla) until you get your 4th total heart. (Max your Charisma so you get a bunch of dialogue attempts. After about 30 times you should be all set) Once you max it out the 4th heart needs the rough dialogue (tell her to be a pet, don't test me etc) to turn purple. At four hearts you can pretty much order her whatever you like without risk, except taking off her crown as it can only be done with the collar.
When you max out the hearts in Day 1, proceed to Day 2, and peek before you open the door. You can see her masturbating then unlock using the key.
Just exhaust yourself and fap until you get to the next day.
In Day 3, you will have max hearts, just keep using rough dialogue or spank her from behind (change position through dialogue too) until you can see the hearts turn purple.
At this moment you can hover your cursor to the right side where you can pick to use the collar. Proceed with it to unlock the Slave ending. You can also still back out if you chose to use the collar by choosing "forget it" on the next choice. This will show you how the MC won't rely on tools to get the female. Finish inside and unlock Good ending.
To unlock the bad ending, simply end the game with lower than 4 hearts.
EDIT: It also has good ass beats too. Went for the H, stayed for the music lol