Masaru is receiving private tutoring from his childhood friend, the older Haruka Usami. They've always been close, and whenever she comes home, his heart starts to race. One day, with his mother out shopping and their study session nearly over, a sudden downpour begins. Haruka can't return home due to the rain, and while talking to her mother on the phone, she gets soaked in the garden. At that moment, her sheer bra becomes visible, and her thighs glisten with rainwater—Masaru can no longer hold back and confesses his feelings.