Oniichan wa Oshimai!

As this series starts Mahiro Oyama is a young man, a lazy otaku, who spends his time playing erotic games and lives with his school aged sister Mihari. She is a scientist whose latest experiment has had a strange effect of Mahiro... it has turned him into a young girl! Now he is about to discover what it is like to be a middle school girl. He is determined to change back but that won't be easy

I though this series was a lot of fun. The concept proves to be a lot of fun and features less fan service than one might fear. Each episode provides plenty of laughs. The characters are likeable; as well as Mahiro and his/her sister there are a variety of friends she makes after starting school. The animation and character designs are good; the fact that they are cute rather than sexy avoids things getting disturbing in certain scenes. Overall I found this to be a fun series; definitely worth watching.

These comments are based on watching the series in Japanese with English subtitles.