Hiroomi Tosaka (登坂広臣, Tosaka Hiroomi, born March 12, 1987, in Hamura, Tokyo, Japan) is a Japanese singer and actor. He is a vocalist of the J-pop group, Sandaime J Soul Brothers He joined the group after winning the Vocal Battle Audition 2 alongside Ryuji Imaichi. As a member of Sandaime J Soul Brothers, he has received the Japan Record Awards twice.

Tosaka debuted as an actor in the 2014 film Hot Road, for which he won the Newcomer of the Year Award at the 38th Japan Academy Film Prize. In 2019, he starred in Yuki no Hana ("Snow Flower"), a romance film based on Mika Nakashima's famous song of the same title.

In 2017, he debuted as a soloist with the digital single "Wasted Love", while remaining a member of Sandaime J Soul Brothers. For his solo activities he uses his birth name stylized as HIROOMI TOSAKA. In April 2019, he released "Blue Sapphire", the theme song for the film Detective Conan: The Fist of Blue Sapphire (名探偵コナン紺青の拳(こんじょうのフィスト)) included in his single "Supermoon" released on April 10.

On February 20, 2021, as he moved his solo project to his own company CDL entertainment(LDH Records), where he can produce on his own, he changed his stage name as an solo singer into ØMI.

On October 15, 2021, he released the digital single "ANSWER ... SHINE". The song "You (Prod. SUGA of BTS)" on this single was produced by SUGA from BTS. It topped iTunes Top Songs Chart in 42 countries and regions around the world, and ranked No. 3 on Billboard World Digital Song Sales Weekly Charts.