[Sides]

Originally Posted by VentAileron

Spoiler for Response:

Recall that Menma is unable to write anything outside the secret base, thus the only way to convey her words to not only Jintan, is to write something while at the secret base (or write something and bring it outside of it, but I doubt they'll do that. ).

I though it was because it has to be connected with her in some way, like the timber beams in the secrete base or her diary. Now you got me interested.