This script does a lot of simple things, like remembering what volume you have previously set to your audios, sync the audio volumes as if they are one (including mute), add space bar and media button keyboard shortcut support to play/pause the audio, add volume change keyboard shortcut through Add (+) and Subtract (-) keys of your numpad. There's also a function to hide furigana (so it only appears when you hover the mouse over the paragraphs).
