Fifteen-year-old Yamada has just entered high school and is gung ho about achieving her ultimate goal: to have one hundred sex partners! There’s just one problem: she’s a virgin, and she hasn’t even had a boyfriend! To get the ball rolling, Yamada decides to target a shy boy named Takashi from her school; but even though he is also a virgin and she ruthlessly aggressive with her feminine ways, it’s not as easy as Yamada hopes. Though they begin to have feelings for each other, will Yamada and Takashi ever get past first base?
Both animes have a huge amount of sex jokes and takes part in a Highschool. The main difference between them is that B Gata H-Kei is more romance driven while Seitokai is just random humor. If you liked Seitokai Yakuindomo be sure to check B gata H Kei.
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?
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.