UWA!!! I forgot this one coz I only saw the anime and haven't read the manga yet XD but yeah give this one a read

I've read some of Velvet Kiss after reading your post (the first 4 chapters, then 2 random in the middle, then the end). I wouldn't call that manga "ecchi with a strong plot". On the contrary the plot is extremely simple and boring, pretty much an excuse for the sex scenes at each and every chapter.

I like it when sex is a logical step in the plot. Like in I am a Hero, wich is an awesome manga. Don't read it for the sex scenes, you'd wait for a while, although there are several. However, the manga is breathtaking and totally worth a read.

Maybe also the definition of ecchi is a bit twisted in my mind, and I confuse it somehow with mature.

However, I'm totally with you on Prison School. It's completely twisted, crazy, outragous, funny and ecchi altogether, but in an assumed way.

Serious props for recommending I am a Hero!