Civil engineering student and reknowned bridge otaku Youichi helps a swan stuck on the scaffolding for a bridge under construction, only to be visited that night by Miwa, a beautiful woman claiming to be the same swan Youichi rescued. Miwa stays with Youichi in order to pay back her debt, but he is, understandably, less than convinced that she is what she says she is. But, Youichi not being one to look a gift swan in the beak, or more importantly not one to leave a woman in need hanging, things soon develop in the way you might imagine.
(Then again, maybe not exactly like you imagine...)