After Marius's wedding, the Forge Eizo family returns to a life of normalcy. The season has turned, and with a sweltering summer on the horizon, Eizo decides it's time to construct a water well near the cabin. However, their digging is soon interrupted by a familiar face: the fairy chief Gizelle appears and asks them to meet the mystical master of the Black Forest! This master requests that the family eliminate a terrifying monster—a beast corrupted by stagnant magic that is devastating the forest and its inhabitants. As someone who lives primarily off the land, Eizo feels indebted, so he readily accepts. But...who exactly is this master? And how do they know about Eizo's previous life on Earth?! Can the family successfully hammer the monster into the ground, or will their home become overrun with malignant magical beasts?