Sora-chan marking her territory.
(In his best David Attenborough impression):
"And here we see the wild tomboy, having successfully pair-bonded to her chosen mate, she continues to rub her scent on her male, to discourage any potential rival females.
Our girl, Sora, is lucky. Some tomboys have extended or even unsuccessful courtships due to an endemic genetic defect, Heritable RomCom Protagonist Disease, or HRPD, which dulls affected males' ability to see the tomboy as a potential mate, despite tomboys' excellent coherence in communication with most males. This is not to be confused with the extended courtship ritual of the
Teasy Gyaru, a related-but-distinct subspecies of girl that is concerned more with play and discouraging rival females than outright pair-bonding and mating.
Our Sora has not only claimed her mate, but shows off their successful courtship to the pack. Her continually-flushed cheeks and heavy breathing, despite the mild temperature, confirm that it is instead a symptom of estrus, her body ever-ready to safeguard the tomboy lineage."