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...
Apparently Purple Smoke's virus infects 
your whole body within thirty seconds.
يبدو أنّ فيروس باربل سموك يُصيب
كامل جسدك في غضون ثلاثين دقيقة
Purple Smokes Virus braucht dreißig Sekunden,
um den ganzen Körper zu infizieren.
El virus de Purple Smoke
te infecta por completo en 30 minutos.
El virus de Purple Smoke
te infecta totalmente en 30 minutos.
Le virus de Purple Smoke se propage
au corps entier en 30 secondes.
Credo che il virus di Purple Smoke ci metta
trenta secondi a propagarsi in tutto il corpo.
Parece que o vírus do Purple Smoke
infecta o corpo em até 30 minutos.