Nyuurin ga binkan'na koto ga imouto ni barete waraware nagara sanzan moteasobareru zako chikubi ane 2: Miu Arioka × Ito Akana
The younger sister, who often mocks her older sister’s small bust, waits for a chance to strike back. One night, she finds her asleep near the entrance and discovers her nipples are highly sensitive. The next day, while the older sister is on the phone with her boyfriend, the younger one teases her, triggering an intense physical response. This leads the older sister to privately explore her newfound sensitivity.
