"Best Couple
Hime often gets excited when she's outside her natural habitat, but they are Gensokyo's true and natural couple. By the way, I stol... referenced Yohane-san for Kagerou-san's covered eye look." (Commentary TL taken from Booru)
It occurs to me that since this series seems to be setting up onee-chan and her kouhai as a side-couple, maybe a Akari x Kasumi tag might be warranted? Just a thought.