Juumonji must be the most buff high school student in Japan.
He was described as 185cm and Mayumi somewhere around 155cm (something about her being shorter than her peers), so there should be ~30cm height difference between them.
In this illustration it looks like there's at least 40cm difference between them and his build doesn't exactly help.
Random thought, in Vol.1 there was a colour illustration allowing to measure the rough height of some characters, I'm imagining how it would look like if Azusa (shorter than Mayumi) was standing next to him.
