In the midst of his usual school days with friends, Ryuya and the group accidentally sample an unusual medicinal juice that triggers unexpected reactions. The girls soon notice changes in their bodies that heighten their sensitivity and leave them seeking ways to regain composure. With his older sister Miya among those affected, Ryuya begins helping them manage the effects while exploring options to create a stabilizing vaccine. The episode introduces the sudden shift from their peaceful routine to this new, intimate challenge.