The most scary one is the guy of the stairs... and the most sick one is the one with his dad (and he appears in several of her manga as background character)!!!
Was Kurose really in that restroom... in the begining I thought it was Shirotani using his imagination... but Kurose smirk in the last image makes me feel he is there... I don't think Shirotani can imagine Kurose face!!!
No, Kurose was not there. It was only Shirotani's imagination.
I also had a doubt at first but as soon as we could see Shirtani was indeed alone in the restroom, I understood Shirotani imagined what he wanted from Kurose and what was arousing him.
I had to read the manga in another webpage... the pages in this one appears broken!!!
I got that too.