Yilsia was the unigon that Izroth saved from the secret underwater base. He had a quest to safely return to the unigon to its rightful owner, which is why he left the Phantom of Harmony in charge of Yilsia's security while he was completing the trial dungeon. However, for some reason, the Phantom of Harmony had returned to his side the moment he exited the trial dungeon.
Of course, Izroth checked the quest information and saw that Yilsia was still at a high level of happiness. This is why he did not rush immediately to find out what happened since she still seemed to be safe.
"Reporting, Yilsia is currently with Sir Empyrean and Young Miss Selene. Since Sir Empyrean is with her, I judged that there was no need to worry about her safety. So, I returned to your side." The Phantom of Harmony replied without hesitation.
