Gin-san takes history lessons, and teaches you how to hide your porn mags?
Tsukuyo tries to teach Seita history, the subject he's not great at. However, her training (?) methods end up leaving him scarred, which makes desperate Seita ask Gin-san to take over as his tutor...
the very act of hiding something will 
make something seem off in the room.
حقيقة إخفائك لشيء وحدها كافية للإنذار
 بخطب ما في الغرفة
ao se esconder algo, algo parece
 fora de lugar em todo o quarto.