No respect for Rin. Considering that, I wonder how long Yuu is going to allow him to stay anymore. She might have fun with Nana at her place if the dude wasn't there. As it is, Yuu isn't a huge fan of having Nana meet Rin too many times, I reckon. Nor would they need the audience anyway. However, if you remove the dude, 90% of comedy in the series disappears, plus things would be too smooth and easy for Yuu.