Viktor Krum is known for many things like, being the youngest seeker in the world, or for being the best seeker in the world, even for also being a girl magnet. But the one thing no one ever thought that Viktor Krum could be jealous. It was just unthinkable after all he was Viktor Krum what would he have to be jealous of. But he wasn't jealous of anyone he was jealous of Harry Potter the Boy-Who-Lived, the boy everyone thought would save the whole wizarding world from Voldemort and his Death Eaters. And its not that he didn't like Harry he just didn't like the way Harry always spent with one person he has wanted to speak to since he first saw her when he and the other Durmstrange students arrived at Hogwarts for the Tournament.
But Viktor is going to talk to her before he has to leave and go back home, that's the promise he made to himself. And he's going to fulfill his promise to himself. That is why he's been coming to the library everyday so he can get the courage to talk to her, but everyday she is always in the library with him. Everyday she sits in a desk in the back of the library with Harry Potter sitting next to her. And everyday he has to watch them from a desk near them but with giggling girls watching him, because he to shy to talk to her in front of Potter because he's afraid that might be her boyfriend and if he asked her out they would both laugh at him and she would tell him that she's taken and would never go out with him.
And to the person who know him best and that isn't a lot of people, Viktor is a shy and sensitive person, he wouldn't take that well and would go back in his shell of brooding. But for now he is going to wait and watch her until she's not with Potter anymore and he finally gets the courage to talk to her.