There's some in the Josei genre. It's basically shoujo aimed towards adult women. I really like this one: http://www.mangago.zone/read-manga/nana/
There's also some in ecchi/seinen genres, which are more porny, like this one: http://www.mangago.zone/read-manga/h_mate/
holiday love-it's ongoing
I 2nd nana...but OH MY GOSH this manga and anime made me go insane...and the fact that it's not completed..AHHHH..This is probs one of the hardest decisions u have ever had to make..jkjk but seriously this manga played with my emotions
http://www.mangago.zone/genre/Josei/?f=1&o=1&e= (Josie manga is your best bet when it comes to relationships with sex)
THANK YOU ALL^
Is there any heterosexual mangas so like a shojo or a romantic manga that's like a yaoi. So like shows the sex, relationship development, etc.