Mizuha Kuraoka is a Japanese voice actress and former idol, who began her career after being selected from approximately 10,325 applicants in the 22/7 project auditions in December 2016. She was born on June 21 in Shiga Prefecture. Her decision to pursue voice acting was inspired in middle school by the performance of Asami Seto, who was a high school student at the time.

Kuraoka is best known for her role as Miyako Kōno, a character she voiced and performed as a motion capture actor within the multimedia 2.5D idol group 22/7. She was assigned to this character in May 2017 and remained with the group until her graduation in November 2021. Her work as Miyako Kōno extended across several 22/7 projects, including the television anime series 22/7 in 2020, the variety show 22/7 Keisanchu, and the smartphone game 22/7: Ongaku no Jikan.

Beyond her signature role, she provided the voice for Nozomi in the 2018 web animation Megane no Mahō, a disease awareness project by Chugai Pharmaceutical. She also had minor roles in television anime, credited under the name Kurao in DIVE!! (2017) and Harukana Receive (2018).

Throughout her career, she developed recurring professional relationships within the 22/7 framework. She co-hosted a radio program titled Kura Ten! with fellow 22/7 member Sally Amaki from April 2019 to March 2020. She was also a regular guest assistant on the radio show WashiZaki Ken no Yoru Night x Yoru Night in August 2019 and January 2021. In 2021, she became a monthly contributor to the FM Shiga radio program Catch!.

In early 2020, Kuraoka took a hiatus from activities due to an aggravation of a pre-existing condition, but she returned to work in September of the same year. After departing from 22/7, she changed her stage name to Riko Kuramaru in January 2022 and joined the agency Mucho Pro. She left Mucho Pro in March 2023 due to health considerations and subsequently became a free agent. In October 2024, it was announced that she had joined Mausu Promotion.