Mai Minakami
Mai is the least reactive out of the trio schoolgirls, yet she is probably one of the best pranksters yet. She is very stoic, showing close to no emotion 99% of the time. There are very few instances where she may smile or even laugh. She has a very great sense of humor though, as she is often seen trolling the other characters in the show, with very elaborate pranks.

There isn't much else to say about Mai. Her actions speak for herself.