Ozhianvuna was born in Tallaght to parents of Russian and Nigerian heritage. He began his football journey in the academy of Shamrock Rovers, a local League of Ireland club. In May 2022, he played a key role in helping his team secure a 1–0 victory over Midleton in the Under-13 National Cup Final, held at Turners Cross.
Ozhianvuna made his first senior appearance for Shamrock Rovers on 17 January 2025, entering as a substitute at halftime during a 4–0 win against Usher Celtic in the Leinster Senior Cup.
He debuted in the League of Ireland Premier Division on 16 February 2025, coming off the bench in the 69th minute to replace Daniel Cleary in a narrow 1–0 defeat to Bohemians during the Dublin Derby, which drew a record crowd of 33,208 at the Aviva Stadium. Shortly after, on 20 February 2025, he made his first European appearance, joining the match in extra time against Molde in the UEFA Conference League Knockout phase play-off second leg. His team ultimately lost on penalties.
By April 2025, reports linked Ozhianvuna with Premier League side Arsenal, suggesting a pre-contract agreement that would see him join the club in January 2027 when he turns 18.
Ozhianvuna scored his first senior goal on 18 July 2025, opening the scoring in a 4–0 FAI Cup victory over Wexford at Tallaght Stadium.