The person hiding in the mirror was Illuso from the Hitman Team. Fugo ends up being dragged into the mirror by Illuso's Stand, Mirrorman. Fugo then summons his own Stand, Purple Smoke. Despite Giorno wanting to find Fugo, Abbacchio decides to go look for the key, since that was their mission. However, once Abbacchio finds the key, he also gets dragged into the mirror world...
Since the mirror world 
was undone before I died,
،وبما أنّ عالم المرآة قد زالَ قبل أن أموت
Da sich die Spiegelwelt auflöste,
bevor ich sterben konnte,
Y gracias a que la realidad
del espejo desapareció,
Y gracias a que la realidad
del espejo desapareció,
Le monde du miroir a été brisé
avant ma mort,
Dato che il mondo dentro lo specchio
è scomparso prima che io morissi,
Como o mundo do espelho
se desfez antes de eu morrer,
Иначе я бы не вышел живым 
из мира по ту сторону зеркала