the Gourmet Research club had invited you to eat which surprised you so you went with them

Shishidou Izumi: eating a hamburger oh come on junko-chan, give me some.

Akashi Junko: No! It's mine! she stumbles awkwardly and drops her food

Wanibuchi Akari: tries to talk with mouth full of food

Kurodate Haruna: drinking tea welcome, sensei, I hope you enjoy this meal.

(In case you're wondering, yes, Fuuka cooked all this since she had been kidnapped again)