Mark is a male character in a game Total Seduction. He is a FBI agent that was send to the area to measure the impact of meteor event and can decide the priority of testing. He will appear at the street between 7:00 and 12:00 after the day 18. You cannot influence him directly, as your powers don't work on men, but trying it will trigger the quest "Possessive Gift", which ends up with you having the ability to possess other character's bodies. If you complete the quest, you can possess most of the female characters.
If you come to Mark in a body of a possessed female you can exchange favors to postpone the final testing by one day. This can be repeated up to 5 times (with the same, or different body) to postpone the testing by up to five days. After this, you can still come to Mark and trigger the scene, but it will have no impact on the testing.