Mew was always around the MC growing up. They always saw it flying around.

However…

No one else saw Mew.

They always saw a Meowth. MC’s mom never questioned it. She just thought that Mew was a Meowth that followed MC and the Rival home one day from when they were playing.

MC quickly found out that Mew didn’t want others to know about it, so they quickly stopped saying ‘it’s mew though!’. They didn’t know why Mew picked them, but they still love them. They never saw Mew as a legendary, but just as a friend. They would always follow MC and the Rival around, despite the Rival seeing Mew as a Meowth.

MC doesn’t know why Mew stays. They hope that they continue to stay however..

 ~~~~

This was just a little hc to explain why a kid has a legendary pokemon at the start of their journey, and no one seems to be wondering ‘what the absolute fuck’. Mew probably transformed for others, like for mine I’m hcing everyone else sees it as a Mew. What do you think other people see your mew as?