A few loops in, Shuichi is going to try investigating the mirror. But he doesn't have any useful spells or items to use on it (aside from the +1 from his SHSL talent and anything his INT class may provide), so it'll just be examining it in a completely mundane detective way: looking for anything about it physically that seems noteworthy or odd. He'll also be sticking around until 5pm to see why/how it disappears.
But most important test here: what happens when someone who has no "most desired person" stands in front of the mirror? It WOULD have been Kaede, but since Shuichi has spent the past month under the (completely false) impression that she and Minato like each other/are dating, he's completely given up on his romantic feelings for her. And there's nobody that he desires in a platonic way either, as his desires with regards to his best friend are to make up with him after their disagreement (which he has no idea how to even do and shows 0 initiative towards actually doing in canon), rather than a desire for Kaito himself.
no subject
But most important test here: what happens when someone who has no "most desired person" stands in front of the mirror? It WOULD have been Kaede, but since Shuichi has spent the past month under the (completely false) impression that she and Minato like each other/are dating, he's completely given up on his romantic feelings for her. And there's nobody that he desires in a platonic way either, as his desires with regards to his best friend are to make up with him after their disagreement (which he has no idea how to even do and shows 0 initiative towards actually doing in canon), rather than a desire for Kaito himself.
Any DC is fine.