2007–2012: AKB48 In October 2007, Sashihara was accepted as a trainee for the 5th generation of
AKB48. She was promoted to a regular member of Team B in August 2008. Her first title track single was "
Ōgoe Diamond", released in October of that year. She placed 27th in the 2009
AKB48 Group General Elections, where fans voted for the members to be included in the singer lineups for the next AKB48 single, and was assigned to the "Under Girls" lineup, who would perform on the first B-side singles. She remained in that position for subsequent single releases until the 2010 General Elections, where she placed 19th and was assigned to the primary group, known as , who perform the title track. In August 2009, AKB48 announced that she would transfer to Team A, although the transfer did not occur until July 2010. On December 4, 2010, Sashihara attempted to upload 100 articles in a day on her official blog, with the number of page views reaching 35 million on the same day. In January 2011, Sashihara starred in a half-hour television program titled , broadcast by
TBS, which features her persona. The program was subtitled . Sashihara starred in the
NTV4 drama
Muse no Kagami starting on January 14, 2012. She sang the theme song, "
Soredemo Suki Da yo", which was released as her debut solo single on May 2 on the major record label
Avex Trax. Sashihara produced the idol festival Yubi Matsuri, held at
Nippon Budokan on June 25 and featuring girl groups such as
Momoiro Clover Z,
Idoling!!!,
Shiritsu Ebisu Chugaku,
Super Girls,
Tokyo Girls' Style,
Passpo and
Watarirouka Hashiritai 7.
2012–2017: Transition to HKT48, four-time AKB48 Group General Elections winner On June 16, 2012, Sashihara was transferred to
HKT48 after the tabloid
Shukan Bunshun published an interview with a man who claimed to have had an intimate relationship with her. She stated in response that the man was "just a friend" and that the story was completely false. Four days later, she had a panic attack onstage, and hyperventilated due to the stress. She debuted at the HKT48 Theater as a member of HKT48 Team H on July 5, 2012. Sashihara released her second solo single, "
Ikujinashi Masquerade", on October 17, 2012. The single reached number one on the
Oricon Weekly chart, becoming the third solo single by an AKB48 member to reach that milestone. In 2013, Sashihara assumed the position of HKT48 co-manager and theater manager, while continuing to be a member of HKT48 Team H. Her promotion was seen by some in the media as a confirmation of producer
Yasushi Akimoto's intention to grant her a role in the management of the group due of her production skills, something he had been hinting at since as early as 2010. She produced
SKE48 member
Kaori Matsumura's first solo single "Matsumurabu", with free rein over costume design, lyrics writing, music video direction, as well as choice of music and instrumental arrangement. Also in 2013, Sashihara won the annual AKB48 Group General Elections for the first time with 150,570 votes, beating previous year winner
Yuko Oshima's 136,503 votes and prompting a number of subsequent reprints. The book was based on a series of interviews with Sashihara and recollects various periods of her life and career. It was widely advertised by the media as a
self-improvement volume recommended for working adults. After taking second place to
Mayu Watanabe in 2014, Sashihara won the AKB48 Group General Elections three years in a row with a total of 194,049 votes in 2015, 243,011 votes in 2016, and 246,376 votes in 2017. She opted out of the 2018 Elections, which would be the last such event to be held. In 2017, Sashihara announced the audition for voice actress idols on April 29 and started producing the idol group
=Love (Equal Love), consisting of voice actresses from the Yoyogi Animation Academy. In February, she became member and theater manager of the newly founded
STU48, and resigned on November 25 to focus on HKT48. She also became chairperson of the annual
Tokyo Idol Festival, she would hold this position until she was succeeded by
Neru Nagahama in 2021.
2017–present: Idol production and other business ventures On December 15, 2018, Sashihara announced that she would depart from HKT48. Her "graduation" concert, titled "Sashihara Rino Graduation Concert ~Sayonara, Sashihara Rino~", was held on April 28, 2019, three days before Japan's transition to the
Reiwa era; she commented that she wanted to "do [her] best as an idol" until the very end of the
Heisei era. Sashihara launched
≠Me (Not Equal Me) in 2019 and
≒Joy (Nearly Equal Joy) in 2022 as sister groups to =Love. She won the Lyrics Award in the 67th
Japan Record Awards for the =Love song "Tokubechu, Shite" in 2025. Sashihara is co-founder and producer of the cosmetic brand , founded in 2022 in collaboration with talent agency
Twin Planet and cosmetics manufacturer Koji Honpo, and the
contact lens brand Topards. and
@cosme in 2025. ==AKB48 General Election placements==