Doodooma

"Wanokuni," a country surrounded by high walls, with an enourmous tree in the center. Two brothers, Mana and Shino, live here in peace with their friends and neighbours. However, those peaceful days abruptly come to an end with the arrival of two mysterious women from the outside world… Suddenly, Wanokuni is under attack! With his friends dying around him, Mana discovers that Wanokuni is in fact a giant living creature, and that the enemy have arrived in another giant creature. Here the story begins… the brothers Mana and Shino face a great battle, which will decide the fate of their world!

(Source: Silent Manga Audition)