3rd hidden ending: in the 10th round you can find a key. when you have it, finish the game with 9999C points to see the ending. The key can appear in these places:

At the beginning of the game you have to entertain the brown-haired woman. Search and find her. When you have entertained her three times she will hide.

Hide and seek:
after the "Hide" prompt appears, the goal is to find her. She is hiding somewhere near the colored containers.

If you find her, have fun with her three more times until she hides again. You get C points each time. If you have 9999 points, she hides one last time. Depending on how you played, you will then see one of the endings!

Items can help you collect C points faster. Simply visit the item shop and buy an item.
But be careful, orange items hurt the woman. If the heart count drops to zero, the game is over!

You can buy 1 item per hideout round.

Here are other ways to get C points:
The woman in the shower (100C)
The woman in the toilet (100C)
Blonde woman hiding behind the containers. (100C)
Interact with the pictures (50c)
Extra C Points (100C)
Extra points appear randomly where the floor is green.