Pygmalion

At the National Local Mascot Festival, children all across Japan can meet their favorite local mascots. But as the festival gets underway, it becomes clear that what's inside these costumes aren't people - they're something much darker, with a taste for human flesh. Amid the chaos spreading through the entire country, Keigo Ayahara, his little brother Makoto, and his friend Ako must now fight for their survival and their humanity.

(Source: MangaUpdates)