Duck beamed at hearing Kyouya had a friend, as if it was by her own doing or something similar. He'd said he preferred to work alone, but he still had someone!

"Huh." She watched the letter as if expecting it to do something special. "I guess you're right, Kyouya! I guess we sort of solved the mystery... Though we've ended up with another one..." She struck a determined pose and added, "But we'll solve that one too! Together!"