Basically, Harry gets jealous when Hermione starts dating Krum and realizes his feelings for her. She gives in to his feelings, which causes Krum to get ticked. She realizes she loves Harry, Krum lets her go, yay!
The song is from the kid's film, The zwaan-, zwaan Princess. The creator of this video also used Spike and Buffy as an adult Draco and Hermione. Enjoy!
