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...
If Mirror Man can stop this thing's 
punch even for a moment...
إذا استطاع ميرور مان إيقاف لكمة
...هذا الشّيء ولو لبُرهة
Wenn Mirror Man seinen Schlag
einen Moment lang verzögern kann …
Si Mirror Man puede detener su golpe
aunque sea por un instante…
Si Mirror Man puede detener su golpe
aunque sea por un instante…
Se Mirror Man riuscisse a fermare il pugno
di questa cosa anche solo per un attimo...
Se o Mirror Man conseguir deter
o soco desta coisa por alguns momentos...