I was confused. Why the hell Guards Students did cosplay instead of introducing other students.
They thought like
"We must introduce someone to Satou, but don't want that because..."
"We are afraid another one will take away our share of MALE companionship."
"We can't say we don't want you to introduce someone."
"Neither we can't say don't interact with someone other."
Instead, let's pretend to be different peson, in this way Sou will understand that "Sou doesn't need anyone else, We can be however he likes" or "he will understand we can't introduce him to some other FEMALE"