There were a lot of face-slapping novels, and some of the plots were very interesting. For example, in a world full of power struggles, the protagonists were often forced to slap their faces because of some unexpected events, but they would rise up again after every fall to show their powerful strength and wisdom.
There was also a famous face-smacking novel called "The Founder of the Devil's Path". It was about a world full of fantasy. The protagonist, Wei WuXian, was constantly slapped in the face as he grew up, but through wisdom and courage, he finally became a powerful mage.
All of these novels were very popular, and readers liked their plots and the personalities of the protagonists because every slap in the face represented growth and progress.
The first slap in a novel might be a sudden outburst of strong emotion like anger or shock. It can be a turning point that disrupts the existing situation. The second slap could either intensify the conflict or show a change in the relationship. For example, in some novels, the first slap is from a character who has been wronged for a long time and finally snaps. The second slap might come as a reaction to how the other character responds to the first slap, further complicating the plot.
Toge Inumaki is important too. His special cursed speech ability makes him stand out. Also, the principal of the school, Masamichi Yaga, is likely to be important as he is in a position of authority and has an influence on Gojo and the other students. There could be other characters like the members of different clans that also play roles in the complex web of the story.
I don't know who the author of 'the slap novel' is. There are so many novels out there, and without more information, it's impossible to determine the author.