Their mutual feeling for each other.

This is one of the strong evidences that Jang Keun Suk and Park Shin Hye are definitely a REAL couple in real life until this moment.
Most importantly, these were directly stated by them both and exactly not unrequited.
JKS : "I like her, but maybe she doesn't like me."
PSH : " Her mother likes me, but he is indifferent."
What do you think? I simply love how they connect, and I respect JKS because he is doing his best to protect her and their special relationship.
Credits to the owners and uploaders.