Bitter Virgin - Vol 1 to 3
Summary: Suwa Daisuke is the ladies man of his small town high school, and he has his eye on most every girl, except for one. Aikawa Hinako isn't his type, but when he overhears a deep dark secret of hers, he finds himself thinking of her more and more. [From MyAnimeList]
Impression: This is not a series for people who only want happy endings. Although I've only read up to volume 3 (which is as far as the manga is right now), I have already been brought to tears twice. Now, sad endings are not guaranteed since I don't know how this will end, but you should be able to tell from the summary that this is a darker, more mature series.
Personally, I'm addicted to it. I want to know what happens, I empathize with the characters and I like that the author acknowledges that things don't go according to plan. There are many serieses that just seem to sugar coat things and magically everything turns out good, but life isn't like that and I think if this series did go for a sugar coated look on things, it would come off cheap. The artwork is nice and the fact that this girl/woman type of plot is being told through the boy's point of view is refreshing.
This is not going to be a long series (according to end note of chapter 24), so you don't have to worry about things being drawn out over the course of 20+ books. It actually seems like this will go on for a total of 5 books.
The author is on a break at this point in time, so this is a good time to catch up on the chapters you've missed, but I shall warn you, chapter 24 is a cliffhanger.