Should I tag a relationship if they're being cheated on the entire time?

My main character is initially in a relationship with one character, but cheats on them with another. I will tag Main Character/Other Character as the main relationship tag because that's what the focus is on for the fic, but I feel weird to tag Minor Main Character/Original Partner because it is NOT minor at all, they have scenes regularly and are 'together' throughout the entire work.

Does the minor imply unrequited as the relationship only appears real to one of the characters? Would a Minor Relationship + Infidelity tag be sufficient?