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...
We're going to solve this mystery, 
save Fugo, and defeat the enemy!
سوف نحلُّ هذا اللّغز وننقذ فوغو
!ونهزم العدوّ
Wir lösen das Rätsel, retten Fugo
und besiegen den Feind.
Je vais prêter main-forte à Fugo
et trucider l’ennemi.
Dobbiamo risolvere questo mistero,
salvare Fugo, e battere il nemico!
Temos que desvendar este mistério,
salvar o Fugo e derrotar o inimigo!
Мы разгадаем тайну, 
спасём Фуго и убьём врага!