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...
but he comes up with the most insane 
ideas and pulls them off...
لكنّه يأتي بأكثر الأفكار جنوناً ويعمل على تنفيذها
Aber er hat Ideen, die er auch
noch durchziehen kann …
Pero idea y ejecuta las ideas más locas…
Pero piensa y ejecuta
las ideas más locas…
mais il invente et exécute
des plans de malade !
ma gli vengono sempre delle idee assurde,
e riesce anche a metterle in pratica...
Mas ele inventa um monte de loucuras
e as põe em prática o tempo todo...
Какой безумный план! 
И он сам его исполнил!