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's how the world we live in came to be.
هكذا أصبح العالم الذي نعيش فيه كما عليه الآن
Y ese es el origen 
del mundo en el que vivimos.
Foi assim que surgiu o 
mundo em que vivemos.