This is a reference to the scene at 8m39s in season 2 episode 2 "Hesitation Flute" ("Tomadoi Furuuto", とまどいフルート) which originally aired on October 13, 2016.
Natsuki is on her cellphone trying to meet up with a friend and asks Yuuko to "move". This comic imagines the conversation taking a different route.
Updated
I'll go with youHey.What?HmphAll right, I've decided.What? Chocolate? Vanilla?Chocolate mint, right? Got it.Ahh, actually, wait a secDid you not hear me say "move"?Yeah, yeah. I heard you.I'm gonna go buy some ice cream. You want something?Uhh... you're coming back?Well, in that case, chocolate mintCitrus flavors are hard to pass up...No, a safe choice is vanilla...Or maybe strawberry......ah, but that reminds me of a certain someone's T-shirt, so I don't want that right now...I'll be right back, so it'll be fine.You're trying to meet up with someone, so is it okay for you to leave that spot?You say things like that, yet still have the nerve to order.Are you picking a flavour or a fight?