Fish are a pain to take care of since you have to make sure their living area is clean too. Though, come to think of it, that the water the younger sister is living in would have to be cleaned pretty frequently...
Smash that asshole's head in with the empty fish tank.
Then kill the rest of that scummy class too, including the teacher.
By the way, that title doesn't mean what the author thinks it means. Or maybe it's a translator problem. Regardless, she's supporting herself FOR her gill breathing little sister, not THROUGH her gill breathing little sister. "Through" makes the sentence mean something very different in this context.
I like yuri and all but... I could only read a story like this if I were spoiled the ending first, or like, if the first episode shows the future and then the manga is just a long flashback... because I just can't stand asshole universes and idiotic behavior without karma
the ending i imagine is like that other mermaid manga where the girl ends up eating the asshole girl...b
ut honeslty it looks like the sis is a yandere mermaid...