Flying Witch Petit - 5

Akane teaches Makoto a new magic spell: notebook locking! Akane instructs Makoto to write 13 digits on an eraser and placing it face-down at the center of the notebook. Then, she casts a spell on it. When she removed the eraser, the numbers are gone! Now the notebook is locked. However, Makoto feels like she is going to forget the numbers!