Banger gag that "Problem Child" is interpreted as "Child who asks problems". Since questions in school are called "problems" the joke lands surprisingly well.
At first assumption I thought the giant calligraphy gag would be Shiroyama messing up with a typo or tripping, but I'm glad it was something equally absurd and thoughtful.
Main characters dating from the chapter 1 premise, side characters dating a chapter after their mutual introduction. This breakneck pace would give most rom-com mangaka whiplash.