In the manga, Saiki doesn't have a romantic ending with Teruhashi. The focus is more on Saiki's supernatural powers and the humorous situations he gets into rather than a traditional romance.
Saiki K doesn't really end up with anyone in a traditional romantic sense. The manga focuses more on his supernatural abilities and comical adventures.
If you like a calm and expressionless male protagonist, I recommend the novel "The Dimension of a God" to you. The male lead, Qi Mu, had god-level abilities, but no matter what trouble he encountered, he would always respond calmly without a trace of expression. The genre of the novel was sci-fi and time-travel. There were also many comics, such as heroic spirits in the fate world, magical girls, and other elements. I hope you like this fairy's recommendation. Muah ~😗