Okusama ga Seitokaichou!+!

Both have the same intense ecchi plot where it involves guy having to have do their mates , know what I'm saying, but in OgS, the guy often get's thwarted by another harem member from banging his future wife, while in Souryo, the characters were grwon ups and can do each other, know what I'm saying?  

Both have the same romance where both parties have to keep their relationship a secret from everyone else at school, the exception, Okusama ga Seitokaichou is kinda rough, while Okusama wa Joshikousei was a little subtle.