I like to headcanon that Hiyoko and Kazuichi have exact opposite reactions coming out of meetings with each other's respective in-laws.
Hiyoko gets absolutely showered with praise, Kazuichi's dad won't shut up about how his son got such a pretty girl to bring home, Kaz's mom doesn't stop bringing up how much he wanted to marry a princess growing up, they share the most embarrassing stories about him, Kaz's parents actually find her really funny. Like actually really funny, and she doesn't feel like she's talking to subservient yesmen.
Meanwhile Kazuichi gets the cold shoulder in some super formal get together with Hiyoko's family. Guy is sweating bullets, he's on his knees in stuffy tradwear he spent his entire allowance on, trying to not look like an unsophisticated ogre to Hiyoko's grandmother who's just got the scowliest, most scrutinizing, scowl of all time, Hiyoko's mom smirks like a villain in an anime, and Hiyoko's dad just has a 'been there, done that' look on his face while like 10 other noblemen and family members snicker at him (present due to bullshit political games of course.)
And by the end, Hiyoko would be worried about making a bad impression while Kazuichi just resigns to being fine never looking good to her family. I think Hiyoko would get a little awkward around Kaz's parents with time, wanting to make the best impression and flubbing around them, while Kaz just kinda ironmans his way through future meetings with the Saionji clan and just gets a thick skin to their political machinations - not caring at all as they begrudgingly start to accept that he's there to stay (Hiyoko's grandma secretly loved the lad since the beginning, she was just making sure he'd stay for more than one dinner)
