Ishida and Kimura have been carrying on a discreet romantic relationship for twenty years, meeting only once each month. To maintain their privacy, they manage their work schedules and escape to hotels or traditional Japanese inns called ryokan that feature relaxing hot spring baths. No one, not even their closest friends, knows about their bond. The story follows them on their two hundred and forty first such excursion, a trip that has become a cherished ritual for the mature couple.

The two main characters are Ishida and Kimura, both middle-aged men whose long-term relationship is defined by these monthly getaways. The narrative focuses entirely on them, exploring the quiet intimacy and deep comfort they find in each other’s company away from the pressures of their everyday lives. The setting varies with each trip, but always centers on the hot spring inns they visit, with the soothing baths and carefully prepared meals serving as the backdrop for their time together.

The series is structured around these recurring trips, each one a self-contained episode that depicts a specific stage in their ongoing relationship. The core narrative arc traces not a dramatic external conflict, but the gradual deepening of their connection over two decades. The story emphasizes the warmth and peace they derive from their shared ritual, from soaking in the hot baths to enjoying good food. A notable element is the inclusion of an eight-page bonus story titled Ishida’s 20 Years, which provides a flashback and deeper insight into one character’s personal history across the span of their secret romance. The tone is described as warm, fuzzy, and tinged with a bittersweet quality, focusing on the blurred line between love and friendship in a heartwarming secret romance between two older men.