I've been wanting to write my theory about HaeSica since I read 'Haru' lyrics.
I strongly believe that he wrote the lyrics based on his own experience, and what catch me the most is this part : 

Don’t bring up breaking up, such hurtful words
 

What does it have to do with HaeSica?
Well, you see, they were once a dead OTP. Almost a year and a half with no interactions at all after known as close friends. They weren't afraid to show their closeness on camera until late 2010.

 
But it all change and they've been dead ever since..

until the end of 2011.

Sica initiated the handshake at MAMA, their selca after SMA, their silly hand gestures at MBC Google Wave concert..

The once dead OTP is back alive.

Right after those moments, Donghae's lyrics are being cheesy. 
Could it be because his relationship with Sica is getting better? 
Well, we'll never know.

But in my delusional mind, 'my little girlfriend' Hyuk rapped in Haru refers to Jessica. (biased, I know XD)

This is pure my theory, but if you think about it, it does make sense. (Or maybe it's just because I'm an IceFishies so it all makes sense? lol XD)

P.S. : this is amazing, btw. credit to kati1017 @tumblr