Let the Right One In (2008)

Oskar is a twelve-year old boy often bullied by his classmates. The son of separated parents, he likes spending most of the time alone. One day he meets a girl named Eli, also twelve years old, who had just moved in next door to the compound where he lives. As they get to meet almost every night, the two end up liking each other until finally they realize that they’re in love. The conflict? Eli is a vampire.