Talk with Catherine!

"So... you are Knight of Seiros?" Byleth asked Catherine as he turned towards her.

"Pretty much, yeah," she nodded. "Not to toot my own horn, but I am one of the best, in direct service to Lady Rhea herself." Byleth nodded. He could tell she was quite proud of what she had accomplished and her calling in life. "Perhaps you'd like to train with me sometime. I get the feeling we could learn a thing or two from each other. In fact, I'm quite interested to see why Lady Rhea seems so interested in you."

"Actually, that makes two of us," Byleth noted, surprising her a little. "I'm also unsure why she suddenly offered me a job around here. My best guess so far is that it's because my father, Jeralt, used to hold a similar position to you, but I can't help but feel that there's more to it than that."

"No doubt," Catherine replied.

"Think she's a little envious of you?" Sothis inquired as she floated around, pouting slightly that Catherine would be tricky to grope through that armor of hers.

"Probably. She has a clearly high degree of devotion to Rhea, it wouldn't surprise me," Byleth mentally replied. "No doubt Seteth also wants you to assess my abilities too," he told Catherine as they headed to the mess hall.

Catherine let out a laugh. "Hah! You caught me! Yeah, he is a little paranoid about Lady Rhea's safety and image, and rightly so! You'd be surprised how many want her dead, or at least to take advantage of her generosity. I've cut down many who have acted against the Church. I wish I was present when that guy impersonating Tomas made his getaway. He wouldn't have escaped me, even if we did need to take him in alive."

Byleth shivered internally. Yep, Catherine was definitely a knight who took her duties very seriously. He needed to make sure he never even had the appearance of betraying Rhea around her, because if they came to blows, she struck him as someone who might actually be able to cut him down. "... doesn't seem Flayn's in the kitchens today," he remarked as they approached the mess hall doors.

"Oh? How can you tell?" Catherine asked with an amused smirk.

"Because there are more people going in than coming out," he replied.

"...yeah, that logic tracks," she laughed. "I'm not a picky eater, mind you, but that girl could make stuff that even rats would run away screaming from."