Most Helpful Guy
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Most Helpful Girl
Find out who they are seeing and where they usually go. You can confront then. Or if you don't want to do that, I would seek out evidence. Is it possible you can find messages between them? You'll need to have a plan.
Plus try to figure out if it's possible that the person is just busy with stuff. It could be that they are just working on some things and they're not cheating at all.0