Rina Akiyama, born September 26, 1985, in Tokyo, Japan, is a multifaceted Japanese actress, gravure idol, and tarento who rose to prominence through her memorable roles in the Kamen Rider franchise and earned a unique distinction as the woman with the "Best Butt in Japan." Her career, spanning over two decades, has made her a recognizable figure in Japanese pop culture, particularly among fans of tokusatsu and video games. Akiyama’s journey from a young model to a celebrated performer is marked by a blend of on-screen charisma and a distinctive, lighthearted public persona.

Akiyama began her entertainment career in the early 2000s, initially finding work as a gravure idol and tarento—a Japanese term for a multi-talented media personality. Her big break came in 2001 when she was cast as Mana Kazaya in the popular superhero television series Kamen Rider Agito. This role introduced her to a wide audience and established her as a recurring presence in the Kamen Rider universe. Years later, she returned to the franchise in a more prominent capacity, playing Naomi, the cheerful and resourceful waitress of the time-traveling DenLiner, in Kamen Rider Den-O. Her performance as Naomi, who assists the titular heroes across time, endeared her to fans and solidified her status as a beloved figure within the series’ extensive lore.

Beyond her television work, Akiyama expanded her reach into the world of video games with a notable cameo in Metal Gear Solid 3: Snake Eater. In the game, she appears as a pin-up model on a poster featured in one of the game’s levels, a small but memorable detail that delighted fans of both the actress and the acclaimed stealth-action series. This crossover into a major international video game franchise highlighted her growing recognition beyond Japanese television.

In 2007, Akiyama garnered widespread media attention when she was named the woman with the "Best Butt in Japan," a title that led to the affectionate nickname "Oshirina"—a portmanteau of "oshiri" (butt) and "Rina." This playful accolade became a defining aspect of her public image, and she embraced it with humor, often incorporating it into her gravure work and public appearances. The nickname followed her throughout her career, underscoring her status as a pop culture icon with a unique and endearing brand. Throughout the 2010s and beyond, Akiyama continued to work in television, film, and gravure modeling, maintaining a steady presence in the Japanese entertainment industry. Her enduring popularity among Kamen Rider fans remains a testament to her contributions to the franchise, and she is frequently celebrated at fan conventions and retrospectives. While she has taken on fewer leading roles in recent years, she remains active as a tarento, appearing on variety shows and in special events, ensuring that her legacy as a versatile and beloved entertainer endures.