Older sister Riko and younger brother Akira, who lost their parents in an accident, vowed to live side by side. At that point, his uncle Ginji approached him aiming for the insurance money left by his siblings. The gentle Riko cannot resist and is robbed of her passbook and seal. Akira tries to take revenge on Ginji, but Riko, who was threatened by being killed in return, decides to dedicate herself to Ginji.
