I couldn't care less about all the het parts of the story, or this Botan person trying to somehow take the moral high road about cheating (somehow it's her sisters' faults, for telling the married man's family that he was cheating with her???).
I was here for what looked like it might be a trans-positive lesbian relationship... which ended up only barely teetering on the edge of being trans-positive in the end! Wowza!

https://dynasty-scans.com/chapters/mermaid_line_ch06
You may want to read this one, and the second part.