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'll be able to tell immediately! Get it?!
!سأتمكّن من معرفة مكانه فوراً! هل فهمت؟
Ich merk es ja sofort. Klar?
¡La encontraré de inmediato!
¡La encontraré enseguida!
Je vais la retrouver, pigé ?
E mi accorgerò subito di qualsiasi
tua mossa! Capito?!
Eu teria percebido, ouviu?
Я мигом его найду, понял?