Hmmm . . . the lack of punctuation in that subject line makes for an interesting set of possible interpretations.
One might be that MarkyMark thinks that Cap owes him for some reason . . . but then that's absurd on its face, because Cap never owes anybody.
And then there's this interpretation . . . MarkyMark thinks that Cap should, for some unexplained reason, belong to him. This is at least plausible . . . we'll have to let Cap weigh in on whether that's an acceptable arrangement for him . . .
. . . which it might be only because we all know that once Cap "belongs" to someone, that someone actually will belong to Cap . . . .