His seriousness isn't a sign of him being bland and it actually tend to make for cute funny things like his detective occupation that he take very seriously but end up from the outside as a kid playing which is cute and sometimes even goofy
Kei seems to be the most affected by the breaking up of KINGDOM and even if he's happy with étoile he keeps holding some feelings about the situation, while the other 2 seems to have truly moved on.
Some male anime viewer be like : "Girls watch anime because of pretty boys without caring about the plot it's so sad "
But the truth is... They are the ones who refuse to watch certain anime because of pretty boys or even cute girls without giving a chance to the story 🧐