>>109578432>Star inevitably gets bored
It was pretty much established that this is the best relationship for the both of them. They knew this from the start it jus took some time for them to realize.>like she did with Tom).
She gave up on Marco with a lot of guilt and despair, saying goodbyes, ready to leave that part of her life behind on Earth. She didn't expect him to come to Mewni. She thought he left Marco with a pretty good life, so she moved on with hers.>Star of course will later come crawling back
They'd rather die than be apart. That's why they both stayed behind in the soon to be destroyed magic realm.>, only to find Marco with Janna.
Janna gave her life so that Marco could catch up with Star.