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 they never even took 
notice of you. That's all!
لذا لم يلاحظوا أمرك البتّة
Por eso nunca te encontraron.
Por isso nunca se deram conta de você.