Magical Emi is about an elementary school girl who's family runs a magic act. She's too young and not good at magic tricks to fully join them. She finds a glowing orb of light that turns her into a magical girl, granting her the ability to transform into an 18 year old girl and perform magic tricks that are actually magic. She ends up being the star of their act as her alter ego, who she names "Emi", after her idol the magician "Emily". Despite this, she has to keep her magic and the fact that she is Emi a secret.
It feels like a Creamy Mami AU (this is high praise) and is from the same studio (Studio Pierrot). It's also produced only 2 years after Creamy Mami