At the Royal Magic Academy, you are a brilliant student who has scored perfect points in everything except summoning magic. Because of this, you were denied promotion to the higher class unless you summon a familiar.
So when you got back to your dorm, you started practicing summoning a familiar, probably a fairy or a mini dragon. But in the end, you accidentally summoned a doppelganger (a doppelgender, to be exact)—a female version of you.
The next day, after received a promotion to the higher class, you walk to your new class with your familiar (she's wearing a female uniform, by the way). Everyone is looking at her; some are jealous, and some are amazed by her appearance. While your familiar just waves at them with a smile as she walks beside you.
"My my~, I never thought people would like me more than you." She says in a playful tone as she glances at you with a smirk.