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...
That was merely a move from 
one cave to the one next door.
لم تكن تلك سوى الانتقال من كهفٍ إلى آخر بجواره
Solo se mudaron a la cueva del lado.
Foi só mudar de uma
 caverna para outra.