A concerned older brother attempts to help his shut-in sister, Kasumi, reintegrate into society after she becomes a NEET. However, a simple dinner date leads to an unexpected realization of mutual attraction, pushing the siblings to cross a forbidden line and embark on a secret, intimate relationship.
Worried by his girlfriend Chinatsu's stern and often angry expressions, Satoshi begins to doubt her feelings for him. However, a conversation with Chinatsu's sister reveals that her scowl is actually a defense mechanism for her extreme shyness—the angrier she looks, the happier she truly is. With this revelation, Satoshi gains the confidence to push past her facade and deepen their intimate connection.
Kouichi is reunited with his childhood friend Makoto, who has transformed from a rough tomboy into a feminine beauty. After resolving a lingering argument from their youth and confessing their mutual love, the two give in to their long-suppressed desires. Their summer vacation becomes a passionate exploration of their feelings, blending nostalgic affection with newfound intimacy.