Oh no. A trading quest! Kathelia hated trading quests. They were sooooo boring. You had to play errand girl to everyone and their mother. First one place, then the other, then backtrack, then backtrack again, on and on and on. It felt too much like what her sisters wanted her to be doing. And beyond that it took forever and there wasn't any challenge or strategy to it! You just had to look everywhere, talk to everyone, and write it all down and eventually you'd figure out who to talk to for each thing you needed until you got your ultimate result, which was a bunch of stupid keys in this case. 

Kathelia just put her head in her hands and leaned on Kyouko for support as she despaired at this. 
[Look closely: 3+2=5. Miss. My question is "What will happen if I systematically talk to each merchant and ask about the keys for the door?" I find out the hard way. Also the curse advances.]