I'm sure this isn't the case, but I like to think that hypno-slave Reimu is still conscious on some level and is purposefully giving really good head to attract Marisa's attention and help via the guy's reactions.
Marisa:N-No I haven't. She's probably taking a walk or somethin... Guu...No, it's nothing. Hahaha... Fuuhiiii....Hyp--nosisWhat was that? Are you alright?Hey, you haven't see Reimu have you?