Ok, great manga. It's hard to find but definitely worth the read. The main character is a girl who's worked under this organization since childhood. She's essentially a genius who has NEVER failed a single mission. A lot of the manga is comprised of separate missions. Towards the middle of the series, Shingo, another character enters. Here begins an actual plot in the story. It's a love story (but a lot more on the action side and not mushy or gooey at all). Shin go lives in the regular world. Will the two of them really be able to get past that barrier? I mean, #9 carries the weight of the world on her shoulders, as well as being able to change the fate of the world.
This manga really is good. I personally would rate it a 10. Even if this review doesn't make it sound that appealing, I urge you to at least read the first 2 chapters before rejecting it. It'll definitely be worth your time.
Sorry! This is only my second review ever. Seriously, try it!