It always bugged this troper that Yuu Tobita's feelings for Mikan were never fully explained. Word of God says that he has a crush on her, but that fact has never been brought up at all in the story. I just don't get why Tachibana Higuchi would mention this if it has no purpose (then again, she gives a lot of minor characters detailed backstories).
It shows him being a shy boy loser. What's the next level down from Hopeless Suitor?