Being already viewed as one of the brightest hopes from the Finnish champions academy, he scored his first goal in his 2021 season debuts, during the 4–2 home championship win against FC Honka on the 24 April 2021.[8] By the end of May, he became a regular starter with HJK, scoring another goal against Ilves, while still aged only 17.[10][11]
Royale Union Saint-Gilloise
On 29 September 2022, Belgian side Union SG announced that they had reached an agreement with HJK about his transfer. He joined the Belgian side on 1 January 2023 on a deal until 30 June 2026, for an undisclosed fee,[12] with HJK securing a sell-on clause.[13][4] He officially made his debut for the club on 8 January against Anderlecht, as a 77th-minute substitute.[14] Terho scored his first goal for the club on 20 April 2023, in the first leg of the 2022–23 UEFA Europa League quarter finals against Bayer Leverkusen. Despite his goal, his team lost the game 4–1 (5–2 on aggregate), and were eventually knocked out of the competition.[15] On 23 April 2023, Terho scored his first goals in the Jupiler Pro League, a brace in a 4–2 away win against Kortrijk.[16] In 2024, Terho and Union SG won the Belgian Cup and the Belgian Super Cup.
SC Paderborn (loan)
On 1 January 2025, it was announced that Terho was loaned out to 2. Bundesliga club SC Paderborn 07 for the remainder of the season with a purchase option.[17][18]
OH Leuven
On 3 July 2025, Terho signed with Belgian Pro League club OH Leuven on a deal until 2028 for an undisclosed fee.[19]
Sparta Rotterdam (loan)
On 2 February 2026, it was announced that Terho was loaned out to Eredivisie club Sparta Rotterdam for the remainder of the season with a purchase option.[20]
Terho played regularly for the Finnish under-17, under-19 and under-21 national teams, before making his senior debut for Finland on 4 June 2024, in a 4–2 friendly defeat against Portugal.[22]
