Marin's second challenge

Preparations
After finishing the first challenge, regardless of outcome, leave Transylvania completely, then return again.

By that time, Marin would prepare the new challenge for you. This time, you would require the full set of servant uniform first. If you still have one from Manor quest, just put it on, otherwise, you can buy new one on the first floor of Manor.

The second trial
Marin would require you to do some chores while wearing the servant uniform... and another special underwear she obtained just for you. The catch is what she would be able to molest you without leaving her room.

Not matter how hard you try, you would fail the moment Pixie would approach you. However, if you bright Rinny with you, she would distract Pixie just long enough for your orgasm to go unnoticed. Even then, you have only 50% chance to pass the test, but fortunately, you can retry as much as you want.

Once you pass the test, Marin would be forced to attend the same challenge herself, allowing you to molest her.

Because Marin would never admit defeat, she would require a rematch, essentially resetting this quest. You can rematch her as much as you want.