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 let's just call it a little give-and-take.
لذا لنعتبر الأمر أخذًا وعطاءً
¿por qué no lo ves como 
un intercambio de favores?
então por que não 
trocamos uns favores?