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 have no way to attack him!
!لا أملُك وسيلةً لمُهاجمته
Ich kann ihn nicht angreifen.
¡No tengo manera de atacarlo!
¡No tengo manera de atacar!
Je peux pas le prendre en chasse !
Non ho modo di attaccarlo!
Não tenho como atacá-lo!
Я не знаю, как мне на него напасть!