While Mari might not *need* coffee to be her usual energetic self, she does like it now and then. She likes tea and hot chocolate as well but coffee is somewhat nostalgic and hard to beat on a cold winter day.
She's terrible at making it though, but people close to her has realized that there's more to it. She doesn't want to learn, so she goes to visit Iris instead to have her make it so they can spend some time together.
Iris is probably the only one with no idea though, and just thinks Mari is genuinely terrible at making it.

By:  Jyinxx