If you liked
Kowarekake no Orgel
|
...then you might like
Planetarian: Chiisana Hoshi no Yume
|
Similar buildup of main characters... both series deal with human and humanoids, both gives feels. If you like simple story with decent depth, give both series (OVAs) a shot.
If you liked
Readiness
|
...then you might like
Maso-Mess
|
Same author same art. Deals with the same theme of hypnosis/mind control. Readiness has a better end than Maso Mess in my opinion. Both enjoyable if you're just looking for a quick fap or like the said themes.
If you liked
Futari Ecchi
|
...then you might like
Love♡Lucky!
|
Same author, both series' characters make cameo appearance in each other. Futari Ecchi, as the name might suggest, focuses a lot more on the sex aspect with a lot of "useful" knowledges - it's like wikipedia for sex. Love Lucky focuses on human relationship, but FE does not lack in that category either. Both series have great comedic moments and of course, great art and great sex.
If you liked
Ayatsuri Haramase DreamNote
|
...then you might like
Oni Chichi
|
Well, the only thing similar are the girls... a black-haired sister and blonde sister with twintails. I highly recommend Oni Chichi Re-born too since it contains no blackmailing and develops the premise quite well. Overall both are quite enjoyable hentai series.