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...
The reason I'm not standing is 
so that I can crouch down.
سبب عدم نهوضي هو كي أتمكّن 
من الجثوم
Ich erhebe mich nicht,
weil ich mich gerade ducke.
No pienso levantarme,
estoy agachado por una buena razón.
No pienso levantarme,
estoy agachado por una buena razón.
Si je suis pas debout,
c’est parce que je reste à genoux.
Se non mi rimetto in piedi
è perché voglio stare qui a terra.
Eu não me levantei
porque quero ficar agachado.
Мне нужно было опуститься, 
вот я и не встаю.