Mars is a shoujo manga series by Souryo Fuyumi. It was published in the shoujo magazine Betsu Fure and ended at 15 tankoubon, plus a gaiden (outside story) volume, making it 16 volumes in all. (the gaiden has three stories, from what i remember--one about mars, and two random others.) The series centers around the love story of high school students Kashino Rei and Aso Kira.
At first, Mars seems to just have some typical shoujo elements--Rei is the "bad boy" type, good-looking, popular with the girls, races motorcycles for fun, lives by himself, and has no idea Kira exists; Kira is the goodygood girl, quiet, shy, sweet, draws and paints in her spare time, and lives with her mother. She's seen Rei around school for some time now, but dislikes him precisely because of his bad-boy reputation. The two of them couldn't be more different.
The shoujo elements listing ends, however, as the story unfolds. It seems their paths are meant to cross when Rei stops to ask Kira for directions to a hospital one day, and ends up with one of her drawings on the back of his map which sparks his curiosity about her. Despite the superficial differences in their personalities, Rei and Kira find themselves drawn to one another, and begin a relationship which deepens and matures as the plot thickens and dark incidents from their pasts resurface. It's really very interesting to see the way they cope with their problems, rise to the situations, and prove to be able not only to deal with their own troubles and emotions, but also to accompany and help each other through good times and bad.
The series has just enough sap and drama mixed together to make it fit right into the shoujo manga category, but stand far out from the rest of the generic student love triangle stories. ^_^ I like! And hopefully you do/will too, despite my long runon babbling. ^_^;;;