Born in Zarautz, Gipuzkoa, Basque Country, Otermin finished his formation with Real Sociedad, and made his senior debuts with the reserves in the 1997-1998 season, in Segunda División B. In the 2000 summer, he moved to neighbouring Real Unión also in the third level
In July 2003, after being deemed suplus to requirements by manager Miguel Ángel Sola, Otermin cut ties with the Txuri-beltz and joined Girona Football Club in the same category. He eventually returned to Real Unión, and played 29 matches during the 2008-2009 campaign, which ended in promotion. On 19 December 2009, aged 32, Otermin appeared in his first game as a professional, starting in a 0–1 away loss against Civil Defense Numancia for the Segunda División championship.
He acted mainly as a backup to Javier Jauregui during the season, as his team was eventually relegated back.
