Oh Brother, Oh Sister!

小野寺の弟・小野寺の姉

Since their parents died at an early age, Susumu and Yoriko have lived together. Susumu is now 33-years-old and Yoriko is 40-years-old. Both of them have yet to marry. They are like most siblings and they rely on each other. One day, Susumu and Yoriko receive a letter that is sent to the wrong address.