Gotou's "Gotou Vision" is reality, everything else is Unreliable Narrator
When Gotou sees Yokoi doting on Seki or staring at him lovingly, she is seeing what is really going on. Yokoi's narration and story of her trying to keep from being distracted by Seki is all a lie to cover the fact that she is crazy for Seki.
The series takes place in the same world as Psychic Squad
Seki is a esper whose power is to make most people ignore him as long as they're not specifically focused on him. He awakened to it at a very young age, which is why he got used to do whatever he wanted during class without getting caught.
Yokoi is either partially immune to his powers, or just sufficiently strong-willed to resist them. She's probably related to Level 7 esper Shiho Sannomiya given how much Yokoi looks like the latter with her hairdo from elementary school.
