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...
I knew you'd say that, so I added 
a little trick to the dominoes.
تكهّنتُ بقولك هذا، لذا أضفتُ حيلة صغيرة إلى الدومينو
Lo supuse, así que le agregué 
un truco a tus dominós.
Sabia que você diria isso, então 
coloquei um truque nos dominós.