Junpei, tasked with a last-minute onsen getaway with his aunt Mizuki instead of his injured mother, finds himself harboring secret desires towards this alluring relative. While initially dismissing any romantic possibilities, a twist unfolds as they share a private bath, leading to unexpected propositions. Little did Junpei anticipate Mizuki's request for a romantic entanglement, stemming from her own feelings of loneliness amidst her husband's infidelity, sparking a complex and forbidden relationship between them.