Demon Slayer is a manga (japanese comic) created by Koyoharu Gotouge, which was serialized in Weekly Shounen Jump magazine. The anime adaptation is made by studio Ufotable.

Here's the full story.

Nezuko Kamado is the sister of Tanjirou Kamado, the protagonist of the series. She turns into a demon after their family was murdered by a demon. One of her ability is to grow like an adult or shrink like a kid. So this drawing of mine here is her shrinking into a kid and run! :)