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...
Still, I had no idea something 
like that happened to our planet.
لكن لم أكن أدري بأنّ أمراً كهذا حلّ بكوكبنا
Sin embargo, no sabía que algo así 
había sucedido en nuestro planeta.
Mesmo assim, não sabia que uma coisa 
dessas tinha acontecido ao nosso planeta.