Sending messages in New Edo is quite a complex art. The way you send your message says something different about the sender, the receiver, and the message itself.
Everyday messages are sent through the Line system (analogous to our cellphones.) Of course these messages are expected to be read and sorted through by government officials, so no one ever sends anything really important through them. Of course, only middle and upper class can afford to use a Line, and so the poorer working class do not know much about this form of communication.
Romantic messages are sent scrawled on fans through specially selected intermediaries. As privacy is of the utmost importance with romantic messages, these are not often intercepted. Typically only the upper class use these messages as a form of courtship, and thus are not grounds for suspicion.
If secrecy is necessary, a message might be sent any number of ways. The most popular among the upper class is to use a romantic message as a ruse. While romantic messages are not considered suspicious, they are not invulnerable to being read. The romantic message is used as a red herring, and when the fan is folded a certain way, a new message is revealed. The sender and receiver will have worked out the exact folds necessary to reveal the message beforehand. If it is an emergency, the message is written in parts along the insides of the spine of the fan, then the regular message is reattached. This is, of course, not as secure.
The only method the working class use to send a message is by having the messenger memorize it. They’ve found it to work quite well.