Flirting pre timeskip

Claude would endeavour to pull Byleth away from her work to engage in mischief of any kind. On the rare occasion he got her alone he would joke with her, floating ridiculous strategies to her to hear her laugh "That's a pretty cute face you're making." He would chide her playfully before she would wander flustered back to her duties

Ignatz would adjust his glasses frequently when around her and would sketch her from the back rows of the class. On rare occasion she would notice the sketch before he could hide it and would give him a flustered compliment before scurrying off

Raphael would assist her in cleaning her office, showing up once a week and lifting her furniture out of the way. She would look away from him, blushing, as he flexed his arms and chest

Lorenz would constantly compliment Byleth on her beautiful appearance, casually telling her she should smile more often. This garnered the opposite effect and she chose to spend several weeks without addressing him which sobered him remarkably. After this instance he grew a little, bothering the other girls less and only remarking to his professor on her marked ability and strategy

Flirting after timeskip

Claude would taunt her mercilessly, calling her her cute and adorable in front of her soldiers. Its good for morale, he would insist, wrapping a casual arm around her shoulder. "Now if we'd been at my place you would have to wear a court dress and I'd have to show you off a little more tamely. This is much better!"

Ignatz had casually insisted she live model for him for a little while now, usually only using it as a playful threat when she was away too long. Her sputtering face would remain locking in his memory and he would insist she stay put while he sketched her darkening face

Raphael like to pick her up, she was much lighter than other things he's lifted before but the heft of her body was reassuring to him. The first time she'd giggled about it, but now being swept onto his shoulder with one strong arm left her a blushing mess. He would hoist her onto him casually in any part of the monastery and whisk her away nonchalantly

Lorenz now freely complimented her for every cute action, pouring the tea with unsure hands, struggling over proper utensil uses and even being naive to the territories of Fodlan. Byleth was just so cute, there was so much she still needed to know and he was happy to guide her tenderly toward becoming his noble bride