Nanako Matsutaka is a freshman in college, who like many normal girls has enrolled in a course just so she can get closer to the guy she likes. Unfortunately, she’s now taking the Pervert Physiology Course and her classmates are far from ordinary. With Michikawa lurking under stairwells to take photos of girls' panties and Mizukoshi cultivating flies in her ears, Nanako's wide-eyed innocence makes her the odd one out in a bunch of depraved perverts. Will Nanako be able to pass the class when she can’t even justify the worthiness of a report on farting in the bath, and will she ever catch the eye of the cunning Konogi?
They are both Ecchi and also have a normal girl mixed with a lot of crazy people.Koe de Oshigoto! is a story about Aoyagi Kanna, a 16 year-old girl who was asked to become an erotic game voice actress on her 16th birthday by her 28 year-old sister at her company.
Both of these series explore adult sexuality and take a look at the taboo. While the animation styles are quite different, both series focus on the unusual sexual preferences of the characters involved. Of the two series, Nozoki Ana is the more explicit and contains a gratuitous amount nudity and sex. However, both series merit credit for their willingness to explore the taboo.
I think if you like really raunchy and perverted jokes both these anime qualify. Hen Zemi has a more simplflied looking art but it's comedy and pervertedness doesn't let you down. It's got it's own share of ecchi just like SYD and the characters will make you laugh or go WTF with their random slapstick humorous moments.