All Japan Women's Pro-Wrestling (2003–2004) In 2003, Mizushima entered
All Japan Women's Pro-Wrestling (AJW) dojo, where she was trained by
Animal Hamaguchi in not only
professional wrestling, but also
mixed martial arts. On December 19, 2003, Mizushima made her MMA debut at an AJW event, losing to Mika "Hari Hari" Harigai at 2:10 in the first round, after being knocked out with
knee strikes. She has not participated in any mixed martial arts fights since. During late 2005 and early 2006, she also made several appearances for the new Ibuki promotion. On June 5, 2006, Natsuki☆Head won her first championship by defeating
Hikari for
Dramatic Dream Team's
Ironman Heavymetalweight Championship, a title contested under the rules that a champion could be pinned or submitted anytime, anywhere, as long as there was a
referee present. On September 24, Mizushima announced that she was changing her ring name to "Natsuki☆Taiyo". On December 31, Taiyo made her debut for NEO Japan Ladies Pro Wrestling, defeating
Fuka for the
Princess of Pro-Wrestling Championship, a title owned by the
JDStar promotion. On February 21, 2007, Taiyo defeated
Amazing Kong and
Toshie Uematsu to win Pro Wrestling Sun's World-1 Women's Championship. She would hold the title for three months, before losing it to
Kyoko Kimura on May 27. While working in Pro Wrestling Sun, Taiyo formed a
tag team with Nanae Takahashi, with whom she would also make semi-regular appearances for
JWP Joshi Puroresu, with the two unsuccessfully challenging
Kayoko Haruyama and
Tsubasa Kuragaki for the
JWP Tag Team Championship on December 9, 2007.
Passion Red (2008–2010) In April 2008, Taiyo and Nanae Takahashi left Pro Wrestling Sun and formed the Passion Red
stable with
Kana on the Japanese independent circuit. The stable made appearances for several promotions, including
Big Japan Pro Wrestling (BJW),
Ice Ribbon, JWP,
Oz Academy and NEO Japan Ladies Pro Wrestling, Passion Red made its debut for NEO on August 24, 2008, when Taiyo and Kana were defeated in a tag team match by
Hiroyo Matsumoto and
Kyoko Inoue. In their first six-woman tag team match on October 26, Taiyo, Kana and Takahashi defeated the trio of
Etsuko Mita, Toshie Uematsu and
Yoshiko Tamura. While
feuding with the NEO originals led by Tamura, Passion Red also got involved with rival group Revolucion Amandla of Atsuko Emoto, Kyoko Kimura and
Tomoka Nakagawa. On December 31 at ''Grand Final '08
, Taiyo and Kana faced Ayumi Kurihara and Yoshiko Tamura in a match to determine the number one contenders to the NEO Tag Team Championship. At the end of the match, after a botched Taiyo-chan☆Bomb
, Taiyo legitimately knocked Kurihara out with a kick to the face and then pinned her for the win with the Iguchi Bomb''. The Passion Red duo received their shot at the NEO Tag Team Championship on February 21, 2009, but were defeated by the defending champions, Atsuko Emoto and Kyoko Kimura. On April 19, Passion Red and Revolucion Amandla wrestled to a 30-minute time limit draw in a six-woman tag team match. On May 5, Taiyo defeated
Ray to become the first
NEO High Speed Champion. The chemistry between Taiyo and Ray led to the two forming a tag team for July's Mid Summer Tag Tournament VIII. Though the team was eliminated from the tournament in the first round by
Emi Sakura and Nanae Takahashi, the partnership eventually led to Ray joining Passion Red under the ring name Passion Ray. During 2009, Passion Red was also joined by Kazumi Shimouna and
Yumiko Hotta. On September 20, Taiyo lost the NEO High Speed Championship to
Kaori Yoneyama in her third defense. On November 22, Taiyo and Passion Ray received a shot at their fellow Passion Red members' Kana's and Nanae Takahashi's NEO Tag Team Championship, but were unable to become the new champions. On December 31, Taiyo faced male wrestler
Kenny Omega in a losing effort. On February 14, 2010, Taiyo regained the NEO High Speed Championship from Yoneyama at a JWP event. On March 19, she successfully defended the title against Tomoka Nakagawa at Passion Red's fourth independent event. On June 5, Taiyo made her final appearance for NEO, which would fold at the end of the year. On November 27, Taiyo lost the NEO High Speed Championship to
Leon at Passion Red's fifth independent event. The promotion's debut event on January 23, 2011, saw Taiyo team up with
Yuzuki Aikawa in the opening tag team match, where they were defeated by the team of Iris and Nanae Takahashi. Later that same event, Taiyo worked under a mask and the ring name Passion Nakki, facing nine-year-old Haruka in a three-minute exhibition match. Also in May,
freelancer Yuu Yamagata aligned herself with Taiyo and Yoshiko, forming the stable Trouble Maker 2. On October 27, Taiyo represented Stardom in
Sendai Girls' Pro Wrestling's Joshi Puroresu Dantai Taikou Flash tournament, a
single-elimination tournament, where different
joshi promotions battled each other. In their first round match, Team Stardom (Taiyo,
Mayu Iwatani,
Saki Kashima, Yoko Bito and Yoshiko) defeated Team Reina (Aki Kanbayashi, Aoi Ishibashi,
La Comandante, Yumiko Hotta and
Zeuxis). On November 12, Taiyo unsuccessfully challenged Nanae Takahashi for the
World of Stardom Championship. When the Goddesses of Stardom Tag League concluded on November 27, Taiyo and Yoshiko finished with two wins and one loss, making it to the finals of the tournament, where they were defeated by Yuzuki Aikawa and Yoko Bito, whom they had defeated earlier in the tournament. Five days later, Taiyo made her first successful defense of the High Speed Championship, defeating Io Shirai. On June 10, Saki Kashima turned on Yuzuki Aikawa's Zenryoku Joshi stable and became the fifth member of Kawakatsu-gun. On June 24, Taiyo led Kashima, Yasukawa and Yoshiko to a win over
Kairi Hojo, Yoko Bito,
Yuhi and Yuzuki Aikawa of Zenryoku Joshi in an eight-woman battle of the stables. On July 22, Taiyo and Act Yasukawa were defeated in a tag team match by Kimura and Yoshiko, with Kimura pinning Taiyo for the win. From August 19 to September 30, Taiyo took part in the 5★Star GP2012
round-robin tournament, where she opened up with wins over Kairi Hojo and Miho Wakizawa, before losing to Kyoko Kimura on September 2. On October 27, Taiyo and Yoshiko entered the 2012 Goddesses of Stardom Tag League, suffering an upset loss against the team of Io Shirai and Mayu Iwatani in their opening round-robin match. They, however, bounced back with wins over Eri Susa and Nozomi, and Yuhi and Yuzuki Aikawa to win their block. Taiyo and Yoshiko made their first successful title defense on December 24 against Zenryoku Joshi representatives Hiroyo Matsumoto and Yuhi. On December 31, Taiyo and Nanae Takahashi reformed Passion Red for a special appearance at Ice Ribbon's
RibbonMania 2012 event, where they defeated Muscle Venus (
Hikaru Shida and Tsukasa Fujimoto) in a tag team match. On January 14, 2013, Taiyo and Kawakatsu-gun stablemates Act Yasukawa and Saki Kashima first defeated Nanae Gundan (Miho Wakizawa,
Tsukasa Fujimoto and Yui Yokoo) in the first round and then Team
Shimmer (
Kellie Skater,
Portia Perez and
Tomoka Nakagawa) in the finals to become the inaugural
Artist of Stardom Champions, making Taiyo a triple champion in the promotion. Six days later, Taiyo and Yoshiko defeated Thunder Rock (Io Shirai and Mayu Iwatani) to make their second successful defense of the Goddesses of Stardom Championship. On March 3, Taiyo made her third successful defense of the High Speed Championship, when she wrestled freelancer Kaori Yoneyama to a thirty-minute time limit draw. On March 17, Taiyo and Yoshiko lost the Goddesses of Stardom Championship to Kimura Monster-gun representatives
Hailey Hatred and Kyoko Kimura in their fourth title defense. On April 29 at
Ryōgoku Cinderella, Taiyo made her fourth successful defense of the High Speed Championship against Yuhi. On May 9, Kawasaki Katsushika Saikyou Densetsu was stripped of the Artist of Stardom Championship, after both Kashima and Yasukawa had been sidelined with injuries. On June 2, Taiyo lost the High Speed Championship to Kaori Yoneyama in her fifth defense, ending her third reign at 679 days. On July 15, Taiyo and Yoshiko attempted to regain the vacant Goddesses of Stardom Championship in a one-night tournament. After defeating Thunder Rock, the two made it to the finals of the tournament, where they were defeated by Nanamiho. On August 17, Taiyo also attempted to regain the Artist of Stardom Championship with stablemates Act Yasukawa and Yoshiko, but the three were defeated by the defending champions, Kairi Hojo, Kaori Yoneyama and Yuhi. At the conclusion of the event, Yasukawa turned on Taiyo and Yoshiko and jumped to Kimura Monster-gun. From August 25 to September 23, Taiyo took part in 5★Star GP2013, where she finished with a record of two wins, one draw and two losses, with a loss against Nanae Takahashi on the final day costing her a spot in the finals. In November, Taiyo and Yoshiko became the only team to have taken part in all three Goddesses of Stardom Tag tournaments. The two made it to the semifinals of the tournament, before losing to Kimura Monster-gun representatives
Alpha Female and
The Female Predator "Amazon". On December 29, Taiyo won the High Speed Championship for the fourth time, regaining the title from Yoneyama. Following the main event of the evening, Taiyo challenged World of Stardom Champion Io Shirai. On January 12, 2014, Taiyo celebrated her tenth anniversary in professional wrestling by reuniting with Nanae Takahashi in a tag team main event, where they defeated Mayu Iwatani and Yoshiko. On January 26 at Stardom's third anniversary event, Taiyo unsuccessfully challenged Shirai for the World of Stardom Championship. Following the match, Taiyo announced she would be retiring from professional wrestling on June 1. On February 2, Taiyo defeated Kaori Yoneyama in a rematch to make her first successful defense of the High Speed Championship. Taiyo continued making successful defenses of the High Speed Championship, defeating Mayu Iwatani on April 6 and Kaori Yoneyama in a
two out of three falls match on April 29. On May 3, Taiyo and Yoshiko teamed up for what was billed as Kawasaki Katsushika Saikyou Densetsu's final match together, where they defeated Shirai and Nanae Takahashi. Ice Ribbon, while also working independent events produced by
Chigusa Nagayo and Ray. and in a tag team main event, where she and Nanae Takahashi defeated
Command Bolshoi and Meiko Satomura. On June 1, Taiyo was defeated by Nanae Takahashi in her retirement match.
Seadlinnng (2015–present) Following Nanae Takahashi's departure from Stardom, she held a press conference on June 12, 2015, to announce "", a new professional wrestling production company with Mizushima serving as its senior managing director. Mizushima, billed as "Natsuki Taiyo" (without the star in her ring name), also began working for Seadlinnng as a referee, making her debut in the role at the promotion's first event on August 26. ==Other media==