She has been married to John for 21 years. She was born in Japan, but came to the United States when she was very young. Like her husband, she is very conservative.
In book 26, Mimi passed away and Rioko delivered the eulogy at her funeral.
Rioko has a habit of shouting last minute instructions to Claudia as she goes down the block.
She disapproves of Claudia reading Nancy Drew books. She keeps her daughters' birth announcements in the table beside her bed.
Rioko is very organized and was even certified to teach elementary school in Connecticut. Rioko works at the Stoneybrook library. Riotous also disapproves of her daughter eating junk food. She has 500 dollars of emergency money locked in a chest.
Rioko is the head librarian at the Stoneybrook Public Library.