For true ending
After enter all 6 key to the box and got Tiny bikini, re check the box again. Remember the number on the key, enter the number on the piano once again.
Sister ending, don't give your sister Tiny bikini, if you enter the number less than 3 days on piano and escape on chimney. Got sister wear bikini on sea photo true ending.
Tiny bikini sex ending, if you enter the number from 6 key on piano (7 days), give your sister Tiny bikini, and escape by entering the chimney. You got sex with your sister using Tiny bikini secret ending.