Obutsu wa Shoudoku desu

When Konoe Moyako and her little brother Akira were young, he said he wanted to marry her. Naturally, Moyako decided that her little brother was a complete pervert who was obsessed with her. Now that they're both teenagers, Moyako is convinced that she needs to "rehabilitate" him; however, it seems that the "perversion" is entirely in her imagination, and she can't seem to help turning completely innocent situations into creepy ones in her mind!