Change currency code to symbol
If it is a form, you can use hook_form_alter along with the PHP function str_replace to replace JPY with 円. Let me know if you need further help.

EDIT:

&lt;?php
  function YOURMODULE_form_alter(&amp;$form, &amp;$form_state,$form_id) {
    if ($form_id == 'your_form_id') { 
      print str_replace("JPY", "円", render($content));
    }
  ?&gt;