下半分を見ずに皆さんも考えてみてね

Riddle. This story is difficult to explain without Japanese, sorry.
The teachers seemed to understand it, but the girls didn't understand it until the end.

Try figuring it out before looking at the bottom half everyone.

English:

Riddle. This story is difficult to explain without Japanese, sorry.
The teachers seemed to understand it, but the girls didn't understand it until the end.