Since Mangatron is as of yet absent for the proceedings, I shall beat him to it for the perverted analysis of this week's episode.... MuHuHwaHaHaHaHaHa!!
Exhibit A: On the first day, Kobato-chan's mammery capacity is one not uncommon for he age:
Yet one is inclined to believe that her brother Kodaka has slipped Estrogen into her share of the curry, as after its consumption she seems to have gone into puberty overnight!! Don't believe me?
Exhibit B!!
Rebuttals to this hypothesis claim that the sudden increase in mammary capacity is actually genetic, implying Kobato-chan's long-lost sisterly relationship to Sena, and therby justifying the intense affections of the latter fo the former.
Exhibit C: is quite compelling for one to agree to this hypothesis:
And yet, in the VERY NEXT SHOT that Kobato-chan appears in, which one may safely presume is not 1 hour afterwards in narrative time, she mysteriously shrunk to her original mass, as shown in
Exhibit D:
Hence implying that yes, she may truly BE a Shapeshifting Vampire as she claims after all.
So to summarize, the evidence presented from Exhibits A B C and D suggests either:
1: The presence of added Estrogen in Kobato-chan's cury promoted puberty overnight, suggesting less-than-polite-intentions on the part of Kodaka, who wants to make her physically more accomodating to his carnal desires.
2: That Kobato-chan is actually Sena's long-lost baby sister, loaned for adoption to the Hasegawa family.
or
3: Kobato-chan
is after all the shape-shifting vampire Reisys V Felicity Sumeragi in disguise. She realizes that an abundant mammry capacity is simply not hydrodynamic enough to accomodate swift motion in an aquatic terrain.
KuKuKu...Curioser and Curioser.
PS.
A bonus for all you fellow Sena and Kobato-chan lovers out there: