Jonghyun is tired of Key not paying attention to him and he wants Key to love him, as him and not for the fan service. Finally, Jonghyun looses it and snaps at Key, hating himself for doing something he didn't want to do. He ran to the first spot they met, a bridge and it was where Jonghyun was looking out onto the river.

Key knew that he loved the water, as well as high places.

So why did it take so long for Key to figure out where Jonghyun was?