Responses
Yukina also appears in a Junjou chapter. In fact, they occasionally go back and forth XD
I love it when the mangaka does this~ I think Nowaki has even shown up in a Sekaiichi chapter, the one where Onodera passes out from fever, exhaustion, and malnourishment. He's like, "Pls don't run in the halls~! :D"
I just remembered this, so back April when this was last updated, I was going back re-reading previous chapters and I stumbled across a familiar face, look in the first panel, right behind Yukina
http://www.mangago.zone/read-manga/sekaiichi_hatsukoi/mh/v09/c005/24/
It's Misaki~ :D