The boy came to the girl's home in February after having chatted with her 12-year-old friend on Facebook, according to local paper Norrköpings Tidningar (NT).
He had allegedly already propositioned the pair on the internet but the girls had told him only to come by their house if he promised to stop pressurizing them.
However, arriving at the girl's home, the boy tried to undress the 12-year-old, but failed in his attempts. He then turned to her older firiend, and when alone in the room, he allegedly jumped the girl, held her down on the bed and forced her to intercourse, reports the paper.
In police interrogation, the 13-year-old said she had tried to push the boy off her but not been able to. The 12-year-old also said that her friend had been screaming for the boy to stop.
When the 15-year-old left the flat he told the girls that they were not to tell anyone what had happened, according to the paper.
Although the boy has admitted to intercourse taking place and that he knew the girl was under the age of consent, which is 15 years old in Sweden, he claims that it was never a question of rape and therefore argued for a more lenient sentence.
The 15-year-old argued that it was the girls who were the prime movers behind the incident, according to NT.
However, the court sentenced the boy to 130 hours of community service as well as a fine of 85,000 kronor ($12,080) to be paid to the girl.