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...
So that's the warring states 
era I've heard so much about.
ذاك إذاً هو عصر الولايات المتنازعة ذائع الصيت؟
Conque ese es el famoso período Sengoku.
Então essa é a guerra 
civil de que tanto falam.