Mero was such a cheerful cutie pie, but same as Chihiro, seeing her mother torso crucified like that also traumatized her into being more shut-in.
It was really dumb way for Yuzuna to just abandoning Chihiro and Mero if she loved them so much, Jogoro could make her suddenly fell "ill" then passing away since she was cold and don't need to breathe.
It was obvious they would developed abandoning issues then try searching for their mother, knowing she was "alive" someplace else.
Since Rea doesn't remember Chihiro now, due to her hemispherectomy by Salva, she has lost most of her care of him solost her will to be with him as a zombie.
Well, that was sad... Otoki can reunite with Jogoro now, along with his other wives that is...