Interesting psychological comedy. Aniki has sister that once loved and worshipped him. Now, somewhere during puberty, when the light of societal norms clicked in her head that she could never marry her brother, she built up an emotional wall to prevent her from doing something she might regret, only to go to an extreme, while the part of her that still loves her big brother grew in darkness, alone, starving for his affection. Something kicked of this Newtonian backlash: for every action, there is an equal and opposite reaction. What happened that created her brother-loving double, the physical manifestation of her affection for him that has laid imprisoned, probably since before her Red Rice Day, now has appeared. While her knee-jerk reaction is that there's no way these two could be together, she is more afraid of Uraha letting Aniki know her real feelings for her big brother.