So you definitely could but there are moments in the actual series that have to do with the side couple and the build up to their relationship so I do recommend reading the story to understand the side couple but u dont have to
I would recommend not to skip it because there are a lot of moments of them throughout the main story. And their backstories are explained too which would make the side story make much more sense
Can I just read the side stories for the side couple or am I missing out on some moments from the main?