In this lewd 2D adventure, Frisk and Ralsei navigate the treacherous world of the Undyne region, their journey taking a kinky turn. Frisk's curiosity leads them to a hidden hot spring, where they discover the naked, well-endowed Alphys, who's clearly enjoying herself. Frisk can't help but stare at Alphys' bouncing tits and wet, inviting pussy, while Ralsei tries to maintain his innocence. The trio's encounter heats up, with Frisk tentatively reaching out to touch Alphys' clit, making her moan. But their fun is cut short when Sans appears, threatening to turn their horny interlude into a deadly game.