Isn't Aruji the dude mentioned in the earlier chapter by the gyaru with the shadow monster summon?
Like the dude who would be the MC if the teacher wasn't constantly breaking horror manga logic
@Quaysan Yeah, this side plot is reminding me of "When Supernatural Battles Became Commonplace", where the main characters get powers, but then do nothing but screw around in their school club while the good story was happening in the background.
Aruji is from chapter 3's arujibito koutarou, a character that has yet to be seen outside of a single picture, despite his name being a pun on "protagonist" in japanese.