If Yukio can get his (pardon my language) shit together, then I can see him with Shiemi. Rin and Yukio are obviously jealous of each other, also for reasons aside from Shiemi, but Rin doesn't let it get to him or at least show it easily. Yukio is just an angsty teen mess.
Izumo/Shima though.... I was on the boat after he tries taking her to his brother's gig in that one extra, but after the even more recent developments, i'm all over that.
Oh, and can't forget Mamushi/Juuzou!