Yumi kissing Sensei feels, so, so, wrong. It's like walking in on Sara and Sana stripping on a pole in front of a full crowd at their bar "wrong". (Okay I can see Sara doing that, but not Sana. Never Sana.)
Also for "speculation":
- First image
Yumi: "What the fuck is this shit?"
- Second image
Yumi: "Are you wanting to join the Harem too? Like shit, we have a process for these things Yuki.. "
Yuki: "Wh-What? No.. me and him are just friends and.. nothing else."
- Third image
Yumi: "Then fuck off, and keep your hands off my Daddy, bitch."