At its center is a fairly typical standard of teenage pop fiction, the ugly duckling who suddenly becomes a beautiful swan, but here that transformation isn't accomplished via a makeover or Pygmalion-style coaching, but rather by fairly straightforward weight-loss. The fat girl gets skinny, and is suddenly super-hot.
The girl in question is Serinuma Kae, an avowed fujoshi (here, "a passionate fangirl of anime and manga that objectifies male characters and male-to-male sexuality") who manga-ka Junko draws with a big, round, bun-shaped head, huge glasses over her mole-like tiny eyes and the only body in the whole manga that looks like that of, say, someone you might see in real life, out shopping, rather than an idealized high school student.
Yes, simply by starving herself for a week, Kae is now not only hot, but shockingly hot.
So you can see why this might be problematic. I've thought about if there was perhaps another way around this, without involving actual magic; some way in which a girl who wasn't hot could suddenly turn into the most desirable girl in her school and, well, nothing quite seems to work. A sudden onset of puberty would have to involve younger kids, a makeover wouldn't be dramatic enough and any alternate form of sudden beautification wouldn't tie directly into her mourning the loss of an anime character, anyway.
Kae gets so sad she stops eating, and as a result loses a bunch of weight and becomes attractive–take it or leave it. (She does get some help dressing cute from her best friend Ah-Chan, who shares her fujoshi status, but hides it, while Kae is out and proud).
In a rapid fire sequence, we re-meet the four boys introduced in the first scenes–best friends (and her OTP) Igarashi and Nanashima, pretty boy underclassman Shinomiya and her fellow member of the history club Mutsumi–all of whom now ask her out, more-or-less simultaneously.
That would be Mutsumi, who she was friends with, and who was the only character who recognized her after her transformation, something even her mom and brother failed to do.
"Ah, Serinuma-san," he greets her simply upon seeing the new her. He's in the school nurses office, trying to disinfect the wounds he sustained while rescuing a cat from a tree:
"Changed?" Well, yeah, I suppose you've gotten skinnier while you've been gone...but I can still tell it's you, y'know? You kindness hasn't changed. You're still Serinuma-San.So there's the pair that Junko and her narrative seem to be shipping, even if the protagonist is too distracted by shipping her other suitors to one another to really notice.