@Vini mc is fan, being in any relationship outside shows with the idol is a no go on both sides. Her game being exposed could get her in trouble with her contracts. This could actually create a situation where their current relationship would have to be terminated.
@Dreecko frankly most of that is based on inference from their interactions in the manga and a couple other fictional sources, plus the "purity" obsession attached to idols and at least one weird instance of idols being forced to do some weird stuff for contractual reasons.
That said, one would have to walk on eggshells/ lead a double life for PR reasons while also doing the choreography and vocal training on top of being a high schooler in this girl's case. So, it could easily be a very stressful life, and seems to have led to some rotten hobbies in Mika's case.