Managed to get the third ending.
You will need a sister's sympathy from 71 to 100 and sexual interest from 70 to 90 (it should be less than 100, I don’t know the exact value). You will also need to complete a request for vulgarity (like a blowjob). In this case, the ending works even if the sister remains a virgin (but once the sexual interest reaches a value of about 100, the ending will be "normal").
A relatively easy way to get this ending is: Get the friendly brother and sister ending (second in a row) with a sexual interest value of 70-90. And then load the save on the last 30th day and request a blowjob.
At such moments, there are not enough save slots for "Experiments".
You will need a sister's sympathy from 71 to 100 and sexual interest from 70 to 90 (it should be less than 100, I don’t know the exact value). You will also need to complete a request for vulgarity (like a blowjob). In this case, the ending works even if the sister remains a virgin (but once the sexual interest reaches a value of about 100, the ending will be "normal").
A relatively easy way to get this ending is: Get the friendly brother and sister ending (second in a row) with a sexual interest value of 70-90. And then load the save on the last 30th day and request a blowjob.
At such moments, there are not enough save slots for "Experiments".
