it was ! i am so confused so he was having sex with who the younger was with blank and th older with tamiya ugh help
Toudou Kiaka (older brother, long hair) was banging Tamiya
Toudou Hiroaki (little brother) was banging Itou Hisao (looks like Tamiya, and is a professor in the same department)
I think the most confusing part was the fact that chapter 6 showed both couples having sex. So it looked like Tamiya had sex with Hiroaki and then went and had sex with Kiaka, BUT it was Hiroaki x Itou and then Kiaka x Tamiya. Although at that time the conversation between Kiaka and Tamiya was about Hiroaki. I hope that helps!
OMG! I was seriously about to throw a bitch fit. I totally thought that Tamiya was cheating with the semes little brother in ch. 6. but then I realized that it was another couple. Hahaha I'm such a moron