Eh let's see
Kou-- has some attraction to Ohana, hasn't done much, may get with other girl. Ohana gets sad because she has no idea what to do. The main problem is that he's too far away and both are unwilling to do anything.
Tooru-- He is attracted physically to Ohana and is there. He has a motorcycle. But honestly, being there's not a good enough reason.
Since any pairing makes sense as the last here, I'll just go with Ohana x Nako.
Of course, since this is an Okada script, the least deserving person should win so... *runs away*