Shuu is such a great character. Shuu is the best (male) side character without a doubt
I know I didn't like him when watching the anime- I had the same perspective as Ruri on him. I thought he was just some goofball pervert causing chaos for the fun of it. But that perspective started to change with the episode 'Support', depicting the arc about his 'crush' on Kyoko-sensei. Then I started noticing his tendency to cause chaos in just the right way that things developed for various characters. Ultimately, he was helping in his own way, acting like a goofball pervert so nobody could really tell what he was actually up to. He could see everything happening around Raku, and was doing what he could to nudge things in just the right ways so everyone had a chance to get to know his best bud who he admired so much, and help everybody else get along at the same time.
All those study groups together and other gatherings he prompted... Sure, Raku was the star helping them connect in his unique special way, but Shu was facilitating him by getting everyone together.