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...
B-But Giorno, Purple Smoke's virus has 
already spread throughout your body.
لـ-لكن يا جورنو، فيروس باربل سموك قد انتشر
...في كامل أجزاء جسمك
A-Aber, Giorno, das Virus von Purple Smoke
hat sich in deinem Körper ausgebreitet.
Pero, Giorno, el virus de Purple Smoke
ya se propagó por todo tu cuerpo…
Pero, Giorno, el virus de Purple Smoke
ya se propagó por todo tu cuerpo…
Mais toi, Giorno…
P-Però Giorno, ormai il virus di Purple Smoke
si è già diffuso nel tuo corpo...
Mas, Giorno, o vírus do Purple Smoke
já se espalhou por seu corpo inteiro...
Но как же ты, Джорно?