I also think Toudou's character theme is pretty smart. He could very easily derail the story and make it boring, but adding that weird aspect of him taking things too far with the research, has an effect on the rest of the characters and helps us in exploring the two mains.
Toudou is a type of character who is very common in josei manga — the mainstream hetero sort of josei, I mean. He's the elite young man of the company who is emotionless, inexpressive, all about work, hyper-efficient, and constantly pointing out the mistakes of the MC and forcing her to become better at her job. The MC hates him even though all the other girls at the company like him because he's tall, has cold good looks, is manly and alpha, has good prospects, has an expensive car, etc. etc. Of course he and the MC end up falling in love with each other.
If there's something Shimizu is knowledgeable about, it's manga clichés. No surprise, then, that she should feel uneasy when someone like Toudou is around Maekawa. :P (Oh btw, the expensive car? Chapter 18: check!)