In the first set of bubbles, the character comments that he said there was no need to come pick him up. He also adds that the have done this song and dance many times.
The character replies then that "I was shopping for dinner, so I dropped by"
However, I'm confused of what the character replies here here. Is こき使う used for oneself? "You are very motivated"? Or is it about the other character means to exploit him?
The word 買い出し implies he's going to buy a lot of stuff. My guess is that he plans to use the other guy to the full for his purpose of carrying that stuff, at least that's how the other guy took it.
If his purpose is something else, you would need to provide more context.
I think you just need to see what follows.
From what you provided, it is
the other character means to exploit him?
The 1st and 3rd bubble is by the same character (in the panel).
The 2nd bubble says the character is on the way to shopping, and the 3rd bubble complains, saying that the other character (the 2nd bubble speaker) is full of intentions to use him (the character in the panel) up.
