In 1994, a year for record low acceptance percentage of only 2%, Sakamoto was admitted to the Takarazuka Music School with the highest score. Throughout her 2 years at the music school, she maintained the status as No. 1 pupil (all Takarazuka students and actresses are considered “pupil” until they leave the revue, regardless of their seniority, popularity and stature).

In 1996 Sakamoto graduated as top of her class, and successfully joined the revue. By tradition, pupil would have already decided on her stage name (subject to revue approval), and switch to be addressed by it now. Sakamoto began to be billed as Tomu Ranju. The stage name was suggested by her teacher and family. The first name “tomu” was going to be written in kanji as “人夢”, which means giving people dreams; but the kanji was considered too complicated, so it was changed to Hiragana form “とむ”. The last name “蘭寿” is the kanji form of “l’ange”, French for “angel”. Following Takarazuka customs, she also has couple of nicknames (given by fellow Takarazuka actresses and fans): Tomu (とむ), Mayu (まゆ), Rantomu (らんとむ).

In 2001 she began to be cast for lead roles in novice productions. In 2002, she won her first lead role in the revue’s Bow Hall production of Tsuki no Hokage, sharing the lead role of Jiroukichi with Ayabuki Mao. In the same year, Ranju won the Newcomer of the Year award.

In 2005 Ranju won the Best Effort of the Year award. In 2006, she had her own first dinner show Sensation!, further fortifying her rising popularity and singing skills. In the same year, she was reassigned to Cosmos Troupe as third lead otokoyaku. In 2007, as Yūga Yamato was promoted to Cosmos top star, Ranju was promoted to second lead.

In February 2009, Ranju was cast in the lead role for another Bow Hall production Phoenix Wright (逆転裁判 -蘇る真実), based on the Capcom legal thriller video game Ace Attorney. The production was so well-received that the revue presented a sequel, Phoenix Wright 2 (逆転裁判2 -蘇る真実、再び・・・) just six months later. These 2 productions greatly boosted and attested to Ranju’s popularity and her talent, leading to her first Takarazuka concert “R”ising!! in 2010.

In 2011, as Sei Matobu retired, Ranju was re-assigned back to Flower Troupe as the next otokoyaku top star. She debuted as top star in the Takarazuka production of Phantom.

On October 8, 2013, Ranju announced in a press conference that she will retire in 2014. Her farewell production was The Love of the Last Tycoon / Takarazuka Dazzling Dreams, a musical/show based on The Last Tycoon by F. Scott Fitzgerald. On May 11, 2014, after the last performance of The Love of the Last Tycoon / Takarazuka Dazzling Dreams, Tomu Ranju officially retired and became an “OG” (old girls, referring to retired Takarazuka actresses).

In March 2016, Ranju co-hosted pilot for “Takarazuka Dream Tours” with veteran entertainment show host Shinsuke Kasai (who is an avid Takarazuka fan). The pilot was picked up by Fuji Television, and in June it became a monthly show. The show is shot 100% on location, interviewing the special guest while she’s doing an activity she’s always wanted to do but haven’t had the chance. All special guests are Takarazuka OGs, many top star OGs have appeared in the show, including Ranju’s top musumeyaku (娘役, Takarazuka actresses who play female roles) Ranno Hana, Jun Sena, Sei Matobu, Kazuho So, Natsuki Mizu.

After she got married in 2016, Ranju announced that she will be taking a break from acting. Her last public appearance was attending the premier of Ocean’s Eight in Japan, as she played Danny Ocean in Takarazuka’s musical version of Ocean’s 11.

On September 28, 2016, Ranju posted a blog announcing that she has just gotten married. Initially no information was available on her husband. But in 2017, with the announcement that Shuzo Matsuoka’s eldest daughter was accepted to enter Takarazuka Music School, it was revealed that Ranju’s husband is a cousin-by-marriage to Shuzo Matsuoka – making her a member of the Kobayashi family that founded Takarazuka Revue (Shuzo Matsuoka is a direct decedent of Ichizō Kobayashi)