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...
Seeing her brother like that 
would traumatize her for life!
!رؤية شقيقها على تلك الهيئة ستصيبها بصدمة أبدية
¡Ver a su hermano así le 
dejaría un trauma de por vida!
Ver o irmão assim vai ser um
 trauma para o resto da vida!