The story of this anime is centered around the character Megumi Hayashibara. As such, the plot unfolds around her and isn't increadibly complex. She is, however, quite complex and many peculiar and interesting situations arrise in part because of her particular circumstance. The animation is actually very similiar to the graphics style in the manga (the Japanese graphic novel); as is the dialog. For a 2002 release one would expect a bit more detailed graphics (ex: Wolf's Rain), but it was probably done this way to parallel the manga. The voice acting is exceptional for this anime and is probably one of its best strengths.
This anime is probably most comparable to Ranma 1/2. Although, unlike Ranma, this anime has a much more concrete plotline and is driving towards a more solid conclusion. Also, and this was a surprise, Tenshi na Konamaiki is more funny than Ranma 1/2. TnK's humor is more intense and extreme, while Ranma 1/2 has a more soft and subtle humor. Although, both leave you feeling warm and each are heart-felt anime.