Nika is a high school girl who, when she goes out, acts very stylish with her makeup and clothes done up with perfect fashion sense. At home, however, she is the complete opposite, sporting glasses and a jersey to go with a totally uncool demeanor. She is called the "switch girl" because she has the ability to freely and seamlessly switch between her "ON" mode (stylish self) and her "OFF" mode (unstylish self). However, interesting things will begin to happen when male transfer student Arata enters the picture and she attempts to hide her "OFF" mode from him.
Switch Girl is a drama in the vein of Nodame Cantabile - a show that tackles semi-serious issues (such as the stress of being a teen) but in an outlandish, anime-style vein. The show has the exaggerated expressions and cartoon effects of an anime. So it's fun to watch, but becomes almost asynchronous when attempting to become more serious; it feels like split- personality.
And with a short running time of about 4 hours total, plot lines appear and resolve super fast. So on one hand, nothing drags on ad infintum but the issues also don't seem as serious as their made to be if they get resolved in so quickly and so simply.
Verdict? A fun watch if you want something silly, fluffy and not to be taken seriously. Just leave your brain at the door and you'll enjoy.
Hotaru no Hikari is what happens when a "switch girl" grows up. They're both basically the same sloppy, unattractive lazy girl/woman who changes looks completely into a beautiful girl/woman when they're not at home.