From Naono Holics:

For 20 whole years, Ishida and Kimura have been meeting each other once a month, for a weekend in the hot springs, at first as carefree students on their bikes, later - as professionals with busy work schedules, always as friends, month after month. 241 trips.

Except, their trips are a secret.

Except, neither of them ever married, and nor do they feel lonely because of it.

Except, there are unsaid things between them that want to be said...