The plot is about a younger sister who does almost everything to get the notice of her brother, and her brother is also a pervert, peeking at his sister's panties and stuff. It's very incest-related, especially when there are hints dropping everywhere that both of them likes each other.
But, I think the anime has a bit too much of the bro-complex =( It has exceeded my tolerance when the whole episode is about the two of them. Somehow, the plot seems too shallow for my liking, and maybe a tad too digusting. And that's rare, since I have been said to have a bit of a bro-complex myself.