All these mongs in the comment section, jesus. No, you don't "ask permission." You take context clues. Asking permission is the biggest turn off I can possibly think of, it ruins the mood and just makes the other person think you're a pathetic virgin.
So no, MMC doesn't need to ask, he should simply understand that they're in a romantic situation and the mood is right and she's alright with it. He should keep going until he's uncomfortable or she makes it clear - either verbally or nonverbally - that she's uncomfortable continuing. This is how real human relationships work, people.