Miyaguchi started her professional wrestling career in 1994, working under her real name in JWP Joshi Puroresu. She made her debut on December 4, 1994, in a match against Rieko Amano. Originally working as a "junior" wrestler in not only JWP, but also All Japan Women's Pro-Wrestling and Gaea Japan, Miyaguchi went on to win the Junior Championships in both JWP and AJW. After the end of her junior days, Miyaguchi adopted the new ring name Ran Yu-Yu, which she held for the rest of her career. Under her new ring name, Yu-Yu went on to win the JWP Openweight Championshipin 1999. She remained affiliated with JWP until October 2002, when she officially joined Gaea Japan full-time. In Gaea Japan, Yu-Yu formed the highly successful Uematsu☆Ran tag team with Toshie Uematsu. The two remained together for ten years, winning Gaea Japan's AAAW Tag Team Championship twice, JWP's Daily Sports Women's Tag Team Championship twice, the JWP Tag Team Championship four times, and the Wave Tag Team Championship once, while also winning JWP's Tag League the Best tournament in 2012. On April 30, 2012, Yu-Yu and Uematsu defeated Moeka Haruhi and Shuu Shibutani in Uematsu's retirement match. Following the folding of Gaea Japan in 2005, Yu-Yu began working as a freelancer though effectively making Oz Academy her new home promotion. In Oz Academy, Yu-Yu became a two-time Tag Team Champion with Akino, with the two representing Aja Kong's Jungle Jack 21 stable. On April 29, 2011, Yu-Yu defeated Kong to win the Oz Academy Openweight Championship. After a three-month reign, she lost the title to Dynamite Kansai. Shortly after her longtime tag team partner Toshie Uematsu had announced her retirement, Yu-Yu followed suit and announced that she would retire before the end of 2012. On November 11, Oz Academy founder Mayumi Ozaki was announced as Yu-Yu's opponent for her retirement match on December 9. Having quit Jungle Jack 21 and joined the villainous Seikigun stable on September 23, 2011, in order to get another shot at the Oz Academy Openweight Championship, Yu-Yu reunited with her old stablemates for her final self-produced event, titled Starlight's Regret, on December 2, 2012, which saw Yu-Yu, Aja Kong, Akino, Hiroyo Matsumoto and Tomoka Nakagawa defeat Carlos Amano, Chikayo Nagashima, Meiko Satomura, Sonoko Kato and Tsubasa Kuragaki in a ten-woman tag team match that lasted over an hour. On December 6, Yu-Yu wrestled her final matches for her original home promotion, JWP. First she wrestled Arisa Nakajima to a fifteen-minute time limit draw and then won a twelve-woman main eventbattle royal, where all participants were dressed as her, scoring the last elimination over Kazuki. On December 9, Yu-Yu was defeated by Ozaki in her advertised retirement match, following interference from Ozaki's Seikigun stable. However, immediately afterwards, Yu-Yu teamed with Carlos Amano to defeat Ozaki and Dynamite Kansai, pinning Ozaki for the win in the final match of her career.
