At least we might see Brandi again later, and how do you know for sure Aiko won't join the harem? The realtor definitely belongs in the one shot category though, what reason would we have for running into her again after all. What category does Shawna fit in then, we did have the choice to either give her our real number or a fake one (which is just a dick move) after all.
Too bad, although if there was ever a futa or trans character introduced (which won't happen, as it's not one of the planned tags), it would probably be a one shot character.
For now.
I'm also sad that the MC had a little sister, just for her to be dead, wouldn't just dead parents be enough for the plot, because adding a little sister, and specifically adding the fact that her body wasn't even identified just makes it feel like she's still alive, and will return at some point (as for why only now, she could've had amnesia, and her memories only came back recently), otherwise it's pointless to add that kind of information.