The A-League side looked like they were going to seal their first ever win in the competition until a late collapse
Daniel Stynes looked to have secured all three points for the A-League side as stoppage time approached, but late strikes to Kim In-sung and Junior Negrao at the Education City Stadium saw the Glory shattered.
Glory were on the back foot for most of the match, against a team that featured former Perth defender Jason Davidson at left back, with centre-half Jonathan Aspropotamitis putting in a solid shift at the back.
Richard Garcia’s side defended stoutly however and they got their reward on 71 minutes when Stynes scored his first senior goal for the club with a low drive from outside the area.
Ulsan turned up the pressure in the latter stages of the match and Glory were finally overwhelmed on 89 minutes when Yoon Bit-garam brought down a cross and played it across to Kim to score the equaliser.
Despite being shellshocked by the equaliser, Glory nearly went ahead again straight after through a Bruno Fornaroli free-kick that was superbly saved by Ulsan goalkeeper Jo Su-huk.
However, in the third minute of stoppage time as both teams went for the win, the Koreans struck a decisive blow as Junior clinically volleyed home Kim’s cross to go top of the group at the halfway point of the stage.
Glory have yet to get a point from their three group matches to date and will likely face elimination from the competition if they fail to defeat Ulsan in the return match on Friday.