Masaki and Erina (childhood friends/lovers, with Masaki obsessed with Erina’s breast milk/lactation) head to a private beach during spring break, joined by another couple, Tetsu and Shinobu. The group enjoys the sea and shore initially. While napping on the beach, Tetsu and Shinobu secretly start having sex. Masaki and Erina catch them in the act, leading to all shame being discarded. The two couples openly expose their twisted desires, engaging in mutual exhibitionism, partner-swapping teases, fingering, anal penetration, and intense group sex under the open sky. Erina and Shinobu playfully insult each other while being pleasured, escalating to absolute ecstasy. The episode culminates in a surprising post-climax line about marriage, hinting at deeper commitment amid the debauchery. This builds on the series’ focus on lactation fetish, public/risky sex, and couple dynamics, moving from private hotel encounters in earlier episodes to outdoor group play.