(born September 3, 1993, Tochigi Prefecture, Japan) is a Japanese gravure idol and actress affiliated with Twin Planet. Koike first debuted as a junior idol in 2003. As an actress, Koike has appeared as Sailor Luna in Pretty Guardian Sailor Moon (2003) and Shizuka Nomura in Kamen Rider Kiva (2008).
In the early 2000s, Koike auditioned for Hello! Project Kids but did not pass the audition. When she was 9 years old, while visiting Tokyo with her family, she was scouted at a in an Isetan store. She then started a junior idol career with the DVD Big Brother at age 10, when she was in 4th grade. In 2004, she was cast in her first television drama role as Sailor Luna in Pretty Guardian Sailor Moon. She also played the role of Shizuka on the 2008 Kamen Rider Series, Kamen Rider Kiva. In early 2011, she starred in the short TV drama Onegai Kanaete Versailles (ãÂÂãÂÂãÂÂãÂÂãÂÂãªãÂÂã¦ã´ã§ã«ãµã¤ã¦ "Fulfill My Wish Versailles"), alongside visual kei metal band Versailles.
After graduating from Asia University in 2016, Koike took a two-year break from the entertainment industry to spend time studying English in New Zealand and Australia.