Day One
Day Two
Day Three
Day Four
Day Five
This condition for this ending seems to happen if you don't have enough affection points with Yasumi by the time you enter Day Five.
Choosing to eat the liver burger at the fast food restaurant causes your affection points to decrease greatly so you can try that.
I wonder if she hated it that much...
Or, you can use the choices above. At the last choice on Day Four, if you choose "You can possess me", then your affection points will be at exactly 5 and you'll diverge to the good ending.