the third wheel was a good way to inform us that the mc was a pervert and the fmc knowingly let a pervert near her which helped develop the mc and fmc personalities (or at least tell us more about their personalities) (although the third wheel shouldn't be in the story as much as she has)
Oh wow, didn't expect the male MC to actually legit got quite detective-like skill.
I thought his only qualification is genre-savviness about mystery stories.
Not bad cold reading in the first half 7/10 also (not sure about this one) if he said a different color that was completely incorrect she might have said the actual color that would "benefit" the mc ( she would prob say something close to 'how were you completely wrong?' etc.)