This is just Seto-sama's short story from this collection. It's handwritten so I can't read it well. But I think I got the jist of it.
This is probably Azusa Masaki Jurai (the Emperor). When he was young, Seto-sama convinced him to come to Jurai to train with her. She spent 2 years sweetening him up and at that point, she was like a mother to him. I imagine this was happening in that time period. Eventually he agreed to go with her, at which point he eventually figured out what she's really like. They've had an adversarial relationship ever since, but there's also a strong indication that he's a bit of a Tsundere. So he may secretly like her. For her part, she enjoyed manipulating him into becoming the Emperor.