I'm so glad I'm not the only one who recognized him
During this scene, if you looked in the background of other students stretching, the one all flat:
http://www.mangago.me/read-manga/nekoka_danshi_no_shitsukekata/mh/c007/15/
Is the same scene as this from the side-story:
http://www.mangago.me/read-manga/nekoka_kareshi_no_ayashikata/tr/166552/page/105/
I knew they were all connected, but these two are happening at the same time! Awesome!
he substitute does make an appearance with our calico cat friend and the real school nurse
Lol I knew I recognized the school nurse (not the substitute one but the one with the cat on his shoulders)
He has his own little love story with a werecat. http://www.mangago.me/read-manga/nekoka_kareshi_no_ayashikata/