During the course of the 2022–23 Junior Hockey League (MHL) season, Demidov scored over 1.4 points per game (PPG), leading all skaters.
[5][6] Despite limited playing time with SKA Saint Petersburg to begin the 2024–25 KHL season, Demidov was solid offensively, registering eight points (four goals and four assists) in the team's first ten games.
[9] Following the departure of SKA Saint Petersburg teammate Tony DeAngelo in mid-January 2025, Demidov was selected as his replacement as part of the annual league All-Star Game.
[12] On 4 February 2025, he would surpass fellow countryman Kirill Kaprizov for the most single season points registered by a U-20 player across league history with 43.
[13][14] Internationally, Demidov won gold with his country's national under-18 team at the 2021 Hlinka Gretzky Cup, scoring five points in five games.