From the Animeraider:
Shimano Yuuji is about to head to Osaka from Tokyo to get married, and his friends and co-workers have decided to spring for a hooker for him in a private compartment of the train he's traveling in as a "farewell to bachelorhood" present. The girl? She's 17, and new to the business, but certainly not inexperienced. It makes for an interesting trip. Thing is, this girl is going to show up again in Shimano's life in a most unexpected way!