If life teaches us anything, it is that love sometimes happens in the most unlikely of places, with the most unlikely of people. Koshiro is a run-of-the-mill salaryman who has recently been dumped by his partner. With his heart broken and hope lost, he soon comes to realize that he can love again, once he sets eyes on a beautiful young schoolgirl riding the train. However, there is one catch -- this girl named Nanoka is his sister, who he has not seen in years. Knowing that their forbidden love will always be scrutinized by society; will Koushirou and Nanoka be able to resist the temptation?