Mankitsu Happening

They are made by the same studio so there is similar artwork. However, the main similarity is that it centers around a guy working with a bunch of girls he eventually has sex with. Both series have good characters and could be seen as an extension to the variety of characters to adore. While they both have different approaches, they do start with the same premise. 

Mankitsu Happening all the ecchi-slip ups that Rito is notorious for, but this time it's actually a hentai. 

Both are top tier vanilla hentai titles with solid art and well made scenes by the same studio, which explains why characters from Sexfriend make cameos in Mankitsu. 

Both involve a lucky male protagonist experiencing incredibly unlikely sexual accidents around women. 

- both titles collaboration works - has the same style of animation - similar character design - is around a guy in harem situation - quality hentai scenes