Tomomi Kasai is a Japanese voice actress, singer, and former idol, born on November 16, 1991, in Tokyo, Japan. Her career in voice acting began in 2007 with a significant role as Aoi in the original video animation series ICE. This work was notably produced by Yasushi Akimoto, who was also the producer for the idol group AKB48, creating an early link between her two career paths.

Kasai's voice acting portfolio includes a variety of supporting roles in anime television series. She is credited with voicing Bastemon, also known as Persiamon, in the 2010 series Digimon Xros Wars (Digimon Fusion). Her other anime credits include roles in both seasons of Tentai Senshi Sunred (Astro Fighter Sunred), Antique Bakery, Real Drive, and Slap Up Party: Arad Senki.

Her career is deeply intertwined with her time as a prominent member of the massively popular idol group AKB48, which she joined in 2006 and remained with until her graduation in 2013. This background as an idol frequently intersected with her acting work. For instance, her role in ICE was part of a casting approach that mixed experienced voice actors with young AKB48 members. Similarly, her casting as Bastemon in Digimon Xros Wars was publicized as an AKB48 member taking on a guest voice acting role.

A recurring collaboration is evident with her AKB48 colleague, Tomomi Itano. The pair worked together extensively on the live-action tokusatsu series Kamen Rider W. Kasai portrayed the character Elizabeth, while Itano played Queen, and together they formed the musical sub-unit Queen & Elizabeth to perform the series' soundtrack. This live-action role, along with appearances in several Kamen Rider films, forms a significant part of her on-screen acting career.