Lightning's End (Season 2, Episode 18)

20th episode of Mushishi Zoku Shou.

It is about a boy who was born unwanted because his mother was married to a man she didn't love, she wanted to marry another, but her mother ignored her wish. So the woman attempted suicide while being already pregnant, because she didn't want that child from a man she didn't love, she understood she wasn't able to love the child, either. Her husband managed to save her, and a son was born to them. He was striken by a lightning once, when his mother left him tied to a tree in the garden, although he cried and asked for mercy. So he was infested by a lightning-consuming mushi. Ginko attempts to help them.