Once upon a time, there was a Todoroki sister OC named Hana. She had the same white and red hair as her brother Shoto. Hana was often in the shadow of her powerful siblings. But she had a unique power of her own - the ability to manipulate ice and fire separately, not just together like Shoto. One day, she decided to prove herself. She entered a hero competition at school. At first, everyone underestimated her. But as the challenges went on, she showed her true strength, impressing everyone with her precise control over her powers.
One popular fanfiction with this concept might be 'Twin Flames' (this is a made - up title for example). In it, Izuku being Todoroki's twin sister adds an interesting dynamic to the story. It often explores how their different upbringings, with Izuku in a more normal environment initially compared to Todoroki, shape their personalities and relationships within the UA world.
She could be very reserved, like Shoto. Maybe she's quiet because of the family drama she's witnessed. She might also be highly competitive, constantly trying to prove herself in a family full of strong - willed individuals.
Family is a big theme. Since they are twins, it explores how they are related in the Todoroki family dynamic. There could be issues like acceptance, especially if Izuku was previously unaware of her relation to the Todorokis.
His friends would probably take care of him. Midoriya would be very eager to help, using his kind-hearted nature. He would make sure Todoroki is fed and comfortable.