Youjo Shenki isn't really what I'd call a 'parody', but more of a short 'behind-the-scenes' series featuring Tanya and the main battalion members simply sharing conversations and having a laugh. The animation is very simple, using chibi characters and few frames. It is not meant to be taken too seriously in comparison to the anime, nor does watching it have much benefit - it is simply a little something extra for anyone who wants it. I personally felt some of the episodes were a little boring, but some certainly were worth watching for the amusement. ~Should you watch it?~ If you enjoyed the anime and wouldn't mind seeing a bitmore of the characters, like chibis and light humour, by all means give it a go.