This series in particular was about a new girl coming to the school, and came onto the guy. She tells him they'll do stuff he'll never get to "finish", aka alot of teasing.

the title comes from something like a term for "just before" referring to the just before climax.

i read it a few months ago, and now it's driving me crazy. also it's pretty eechi so fetch my minions

Sundome?

Pretty sure that's it.

And moved to 18+ because the manga in question has some nudity...

thats it, thanks

sorry, didn't think 18+ applied to looking for