Halttunen, 18, appeared in 18 games for HIFK's U20 team in 2022-23, scoring at a goal-per-game pace en route to recording 24 points (18 goals, six assists). He also skated in 27 games for HIFK's Liiga team, tallying one assist, and played for Kiekoo-Vanttaa of Mestis - Finland's second-highest professional league - logging three points (one goal, two assists) in three games.