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...
The mnemonic is "One fire engulfed 
those strawberry panties, honey."
كانت عبارة التذكير "سراويل الفراولة الداخلية
 "خاصّتكِ تحترق يا عزيزتي
"Un incendio calcinó tus onerosos 
y divinos calzones, cariño".
O mnemônico "Um fogo queima cinco morangos
 com oito sementes e duas folhas, querida".