Kemono Jihen - Episode 7 - Beautiful Kumi

Shiki's mother was a beautiful Arachne who died when he was very young. At least, that was the story he heard.

Shiki came back to his childhood home because he felt he was ready to find out the truth of his parents' deaths. When he first arrived, he saw a small girl who looked very much like his mother staring at him in a shop. Shiki's uncle explained how the brothers found Kumi as an injured spider kemono and how Shiki's father died while Kumi was still pregnant with him.

The truth of Shiki's trauma was not that he discovered his mother's dead body. It was that he stumbled into his uncle's "research lab" where he forced Kumi into kemono crossbreeding experiments to make a mutant Arachne that could spin golden webs which had powerful healing properties. We don't know if Shiki's mother is still alive, but the appearance of that little girl shows that Kumi was alive a lot longer than his uncle claimed.