On her way to school one morning, a boy from another school gives Himeno a love letter. The sudden turn of events has Himeno bewildered, and behind her bewilderment likes a traumatic memory from her childhood. What happened in Himeno's past? Himeno and Nozomi have come to Kyoko's house for a study meeting. As they're working, something strange happens...
It's not a bunch of puzzles. 
Memorizing formulas is all you can do.
ليست ألغازًا ما. حفظ
.المعادلات هو كل ما يمكنك فعله
Kein Puzzle.
No es un rompecabezas.
Memorizar es todo lo que haces.
No es un rompecabezas.
Solo tienes que memorizar.
Non è un puzzle. Tutto ciò che puoi fare
è memorizzare le formule.
Não é um monte de charadas.
Decorar fórmulas é tudo o que dá pra fazer.
Это тебе не загадки. 
Без запоминания формул не обойтись.