Hey guys!
I am not from the US, but I lived in DC for 2 months back in 2009 (October+November) and I used to go to a nearby Borders bookstore and browse the Mangas section.
One day I started reading this one and came back the other days to read a bit more.
When I moved out of DC I realized that I had forgotten to write down its name, and its been 10 years that I think about it.

So, I will give the descriptions, but some of them I might not be 100% sure (basically all of them LOL)

From what I remember, the story was around a boy who was at school and came to know/used to hang around with a girl (don't know if he had just me the girl or if they were friends. I believe they had met not that long ago), and this girl would just tease him sexually, A LOT.
Basically, the only part that I remember was him sitting next to a tree, this girl came and sat on his lap (with some sort of school uniform - skirt and stuff). His d*ck went hard, and the girl said, something like "if you think about it, there is just these panties keeping our genitals apart".
I think that pretty soon after that the girl made him sit against the tree (not properly sitting; his back was against the tree and his legs bent 90 degrees - just like in a "Wall sit" exercise), and (if I remember well) sat on his lap again, to see for how long he could hold on before falling, and their genitals "meet", just separated by the panties.

Some other details:

-Pretty sure the girl had black hair, probably short/medium sized in lenght.
-I'm 90 % sure the girl was the cover of the manga
-I believe that it wasn't a One-Shot, pretty sure that I leafed trough other volumes of the series.
-Guy (I think he was the protagonist, not the girl) had black hair.
-No signs of fantasy or whatsoever (very focused on the real world).
-Dont remember explicit sex (and sexual organs exposure), just some teasing. But I could be wrong.
-I am not sure what kind of genre it could be (Most likely ecchi, not hentai- but again I could be wrong)
-Pretty sure both of them were teenagers students (not a teacher - student relation).
-It was published before December 2009, and by the "drawing lines/style" I would guess it was not that old (probably from 2000s to 2009).

Thats all I can remember for now!
Sorry for the long post!

Thanks a lot guys!
Hope we can find it!!

Lots of love
X1
🙂

CAN'T BELIEVE IT, BUT I GUESS I FOUND IT!!
SUNDOME IS THE GODDAM NAME!

This is probably a long shot, and I don't remember that specific scene you mention (although it's been years since I read the series), but could it possibly be Sundome?

YEEEEES!!

THANK YOU A LOT BUDDY!

FOR THE WIN!