Exactly! like honestly why kill Chiharu now, after helping her get back with Seta? why involve Chiharu at all?
like, don't get me wrong, it is a sad story. all she wanted was a family and her husband didn't even tried to get to know her, even if the marriage was something they were obligated to do. and i do understood the little boy Kanji, the son of her husband with his mistress IS most likely Seta, but for him to be the master of the house she probably took him in a child (he could also have come back as an young adult and take the house for himself as a way of "revenge", but that would be her brother's fault or something along those lines)... anyway. IT IS also sad that she had to become the housekeeper of her own home, BUT she had ALL THE TIME IN THE WORLD to get her revenge DIRECTLY against Seta, the (probably) source of her hate, since she works for him for years (probably) and he trusted her. there is NO reason to involve a third party, Chiharu, in this mess. she is not related to their past.
and even IF Ume wanted to make him "suffer the lost of a loved one", he was already suffering when Chiharu decided to leave him the first and the second time. Ume didn't even had to try to help them (BOTH OF THE TIMES) got back together.
anyway, it might be just me, but it just doesn't make sense.
If she wants to kill then I can think of only one reason why she might want this. It is for son to feel real pain that she felt when her hubby took away her happiness and gave it to this guy and his mom in form of family. She may want to give the son taste of real family and take it away. Like her hubby did to her.
Chiharo's death would be her ultimate revenge to break him down.
hum im confused to why ume's story so far would make her want to kill chiharu
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oH IT JUST HIT ME HIS FIRST NAME IS KANJI oh okay he was the son of her husband with the mistress.... but still why chiharu, tho? she could've killed him way back