She was into classical music he was into rock music. They hang out in completely different groups, but a chance at meeting at a party (that they both didn’t want to go to) was the start of their love story. They share their love for not only music but each other.
Cassian would secretly watch Jyn play her violin or piano through the cracked door in the school musical room. He loved how she got so lost in her music.
Jyn would listen to Cassian play his guitar and sometimes he’d try to teach her how to play his favorite songs. He even wrote her a song once.
No one would have expected them to be together, but somehow they fit perfectly.