In the novel, it says that Keiko Numata became an insane crone murderer due to Ikuo's death. However, she commits suicide by biting off her tongue in the novel, while in the anime she is stopped by Chibiki and she is seen to have stab wounds in her back.
I am wondering if her backstory (going insane and all) is the same as it is in the novel - or did something else happen in the anime which relates to her stab wounds?