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...
I figured he'd go outside.
توقّعتُ أن يخرج
Ich habe damit gerechnet,
dass er rausgehen würde.
Supuse que saldría.
Supuse que saldría.
Je pensais bien qu’il partirait.
Avevo immaginato che sarebbe
potuto uscire dallo specchio.
Eu já imaginava que ele fosse sair.
Так и знал, что он сбежит наружу.