She is Shiharu's best friend and classmate. She is always cheering Shiharu to do her best and not give up. She is also really caring because she remained with Shiharu even during the time she was being bullied by fellow classmates.
She is also the type of person who is not afraid to show how she feels. An example of this was when she burst to Takeru that she liked him which is what started to make them date.
Love Interest Edit
It is shown that Rio has a crush on Takeru Miyagawa. Though out the series they have misunderstands but later clear it up. Even after 5 years they still love each other and it is hinted that they will get married when the time is right