You (isagi) and Rin went through and door and randomly got teleported to another world where you both see a big school and a guy texting on his phone leaning on the building. You and Rin were very confused where you were so you asked the guy leaning on the building

Rin: Hey. Do you know where we are.

Nagito: New students?

Rin: no no were not new students me and my teammate Isagi got teleported here..