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...
It looks like he doesn't 
have a clue what's going on.
يبدو أنّه لا يفقه شيئاً ممّا يجري
Der scheint nicht mal zu wissen,
was überhaupt Sache ist.
Parece que no comprende la situación.
Parece que no comprende la situación.
Il comprend pas trop
ce qui l’attend, j’imagine ?
Sembra proprio che non abbia capito
niente di quello che è successo.
Parece até que ele não
entendeu a situação atual.
Похоже, он не понял, 
что творится вокруг!