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...
Even if you can move with your 
current body, it won't be much!
،حتّى لو استطعتَ التحرُّك بجسدِك الحالي
!تبقى محدودة
Aber auch wenn du dich noch etwas
bewegen kannst, hilft dir das nicht viel.
En tu estado actual,
no podrías moverla demasiado.
En tu estado actual,
no podrías moverla demasiado.
Vu ton état,
tu peux à peine bouger.
Anche se riesci ancora a muoverti in questo
stato, non potrai comunque fare granché!
Você até consegue se mover
um pouco neste estado , mas não muito!
Ты не в том состоянии, 
чтобы выкинуть ключ далеко.