Teenage girl(s) is currently living with a single, curious, teenage boy: Lewdness ensues. For some reason, the girls in both anime are thirsty beyond comprehension for dick, and the guy, as pure-hearted as he might be, occasionaly gives into their seduction. If all you really want is raunchy humor with hardcore-ecchi on the side, either of these anime will work for you.
Both have lots of ecchi, and a simplistic plot. They also have a similar art style. In both of them, the main characters are in highschool, and the parents approve of their relationships.
Only difference is that Kiss x Sis is incestuous, while okusama isn't.
Shorthair main heroine with school obligations learn to be a proper "girlfriend". A lot of lewd stuff happens. The difference is that Boku no Kanojo rely on dirty jokes, while Okusama is straight ecchi.
Two girls with similar personalities and looks fight for MC by making hot stuff (Shorthair persistent Ui/Sunao vs Longhair shy Rin/Yuki). While Joshiochi is hentai, Okusama is balancing on ecchi borderline.
Kinky Stuff happens in secret...
Tried to do much honeytrap and sexual acts to keep in company..
Since the romance in each other is still there..
Hanabi and Mugi's indecent relationship is actually similar to Wakana and Izumi ..
+ Both are enjoyable as hell...(endings included)
+ Both have very clingy female leads ( Wakabayashi & Ui )
+ Spreading of Love & Marshmallows!!! ( Marshmallow love!?!? )
+ Male leads ( Hige-san and Hayato ) are funny as hell... ( Hige-san's love for Marshmallows ) & ( Hayato ( extroverted personality )
+ Both are very short cartoons ( OtM is only 3:30 min long & OgS is only 8 mins long )
~ Okusama ga Seitokaichou will be getting second season, but nobody knows if Ojisan to Marshmallow will have 2nd season (I hope it will )
Similarly short series built on a high schooler's love trangle and with heavy focus on fan service, however while Okusama ga Seitokaichou just barely remains on the safe side of ecchi, Araiya-san! goes full hentai.