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...
You gave permission...
...منحتَ إذنَ الدُّخول
Du hast die Erlaubnis erteilt, …
¿Me diste permiso…
¿Me diste permiso…
Tu m’autorises à entrer ?
E così hai dato il permesso...
Você deu permissão...
Ты ещё веришь,