Kiviharju made his professional debut at only 16 years old in the second round of the Champions Hockey League on 4 September 2022 against EV Zug, lining up as TPS's seventh defender.
He made his SM-liiga debut in the opening round of the regular season on 13 September, an away game against Tappara.
Once perceived as a top prospect, the injury and concerns about his size saw his projection slide to the tail end of the first round or later.
[8] At the 2024 World U18 Championship, not quite healed from surgery six months earlier to repair a dislocated kneecap, Kiviharju recorded three assists in five games and led Team Finland with a 21:54 average ice time.
[8] Aron "Arska"[9] Kiviharju was born in Esbjerg, Denmark, while his father, Jani [fi], was playing with EfB Ishockey.