More a problem of density rather than volume. Ironically, the problem of not being able to maintain buoyancy is because her mass is too concentrated. In other words, she's not fat enough lol.
The birds are flying low...
It's gonna rainHow do you know?When humidity rises, the wings of the insects the birds hunt get heavier and they can't fly high up.Meaning air pressure is getting low.Yuyuko is flying low too.That's just because she's fat.I see.