Miyaguchi started her professional wrestling career in 1994, working under her real name in JWP Joshi Puroresu.[2] She made her debut on December 4, 1994, in a match against Rieko Amano.[1][2] Originally working as a "junior" wrestler in not only JWP, but also All Japan Women's Pro-Wrestling (AJW) and Gaea Japan, Miyaguchi went on to win the Junior Championships in both JWP and AJW.[2] 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.[2] Under her new ring name, Yu-Yu went on to win the JWP Openweight Championship in 1999.[2] She remained affiliated with JWP until October 2002, when she officially joined Gaea Japan full-time.[2]
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,[12][13] with the two representing Aja Kong's Jungle Jack 21 stable.[14] On April 29, 2011, Yu-Yu defeated Kong to win the Oz Academy Openweight Championship.[15] After a three-month reign, she lost the title to Dynamite Kansai.[16] 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.[17] On November 11, Oz Academy founder Mayumi Ozaki was announced as Yu-Yu's opponent for her retirement match on December 9.[18] 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,[14][19] 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.[20][21] 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 event battle royal, where all participants were dressed as her, scoring the last elimination over Kazuki.[22][23] On December 9, Yu-Yu was defeated by Ozaki in her advertised retirement match, following interference from Ozaki's Seikigun stable.[4][5] 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.[4][5]