After a particularly bad experience with the bullies, Eli/Abby advises Oskar/Owen that he needs to stand up for himself, and offers him words of encouragement, as well as support if he needs it. The two eventually form a close bond when she notices he is playing with a Rubik's cube, and, because of her fondness for puzzles, Eli/Abby's interest is piqued. As a result of these experiences, he is initially defensive when he first meets Eli/Abby. Oskar/Owen is constantly harassed in school by a group of bullies that enjoy torturing and humiliating him, and he fantasizes of one day standing up for himself and injuring or disposing of them.

One of the few friends he has is Tommy, who is a major character in the book, but is omitted from both films save one fleeting mention by Owen in Let Me In. He resides in Blackeberg, Stockholm, Sweden in both the novel and original film, and in Los Alamos, New Mexico, United States in the 2010 film. In all three works, the character is a 12-year-old boy living with his single mother in a dreary housing estate during the early 1980s. Oskar Eriksson is the name of the main protagonist in both the novel and the 2008 Swedish-language film Let the Right One In, while Owen is the name given to this character in the 2010 English-language film Let Me In.

Novel let the right one in