Gigantis

Story:

Humanity was treated as "prey" on that particular day. High school student Gen resides on the island of Tsushima, which serves as a gateway to Japan's main island. Gen was leading a quiet life with his mother, Misaki, his ill sister, and their loving mother, when a "asymmetrical monster" shows up on the island. On the island of Tsushima, chaos reigns. These creatures devour everything, including humans, animals, and vegetation, and they continuously change. Will humans be able to defeat these mutant beings? Exists any chance?