@undercurses kinda hoping it's the mom, tbh. The logical assumption would be a family member, but I'm more interested in potential idiomatic/local metaphorical details that I might not get because I'm from a different culture than the original audience.
@icarushector I tried searching for such folklore, but all I found was https://www.youtube.com/watch?v=_iI1lqQ0LbQ
Also, help the author out by voting for this manga for an up-and-coming award here by July 5: https://vote.tsugimanga.jp/web/ Basically, go to that site, click any blue button, click the other blue button at the bottom of the screen, log in, pick this manga (near the bottom), and I forget what the vote button looked like, but if you get to to this picture you did everything right!