If Manjiro so much as slightly grab Yu, he's kinda not getting out. Though a punch or two could help.
Then again, the AP difference isn't that massive (Yu fodderized the shit out of the dude who did the 62MJ feat, and only got stronger, well, much stronger when he fought Aaron). With his Dura-Neg, wouldn't Yu be able to kill him with a few attacks, if not possibly one shot him? He fought Aaron, who was pretty much a tank compared to Yu, to the point his punches pretty much did nothing at the start (then he got stronger but meh), but his Dura neg was screwing him up badly.
That said, is Manjiro's fear manip supernatural? I feel like Yu would shrug off pretty much any fear stuff as long as it isn't something supernatural, and by that I mean fear that just works regardless of Will and stuff like that.
I don't know jack about Manjiro's skills, so if he's some skill slop god, that might be a slight problem. Still, based on the pages of both, I'm leaning towards Yu due to higher reaction speed, kinda just amping the **** out, and the dura neg.