I don't know if this was true or not but I heard that in the first life after or Tia died Ruve kept complaining that Jieun couldn't do a good job like Tia did, so now she is back for revenge.
Also Allendis will be the teacher of Tia and Ruve's kids while Allendis will stay single
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I remember that this was the first manga I ever read. Now I finally found it again
So much lost memories are coming back