Episode 19: The Thunder-Fire Dog

Dororo and Hyakkimaru are approaching a pass with a puppy when a monster dog suddenly attacks them. The dog controls thunder, hitting Dororo unconscious with lightning and throwing Hyakkimaru down to the bottom of a ravine. In a village down the river where Hyakkimaru is saved, he learns that dog fighting is popular. When he sees the cruelty happening there, he realizes what the monster dog on the pass is. It must be the accumulated grudge held against humans by dogs that have been treated so badly. More terrifying than the monster is the cruelty of humans that can change even the faithful dog into a monster. Hyakkimaru destroys the monster dog, nevertheless, and buries the corpse with due ceremony. Source: tezukaosamu.net