(Warning: This post may contain spoilers.)
From what I gathered from the first two episodes, Weiss Kreuz is about a group of assassins for hire. These assassins, all men of different "genres", cover up their activities by being florists during the day. (I say "genres" because it feels like they intentionally engineered each guy to appeal to a different group of viewers - there's the innocent young boy, the older somewhat apathetic man, the seemingly emotionless guy who also happens to wield a sword ala samurai, and the generic one you don't notice too much.) All the girls in the neighborhood swoon and fawn over them because they're so handsome and cute, and they have no idea that these guys are really assassins. How's that for contrived? Then there are the events that unfold...
The samurai guy visits a mystery lady friend in the hospital where a little girl mistakes him for her brother who she hasn't seen for some time, and later on the samurai guy discovers that this girl's brother has been killed by the man they were ordered to assassinate. This lady friend he had visited in the hospital was a victim of a hit and run and the samurai guy happened to see the face of the man in the car that hit her. Later on he happened to stumble into that man on an unrelated assignment. Too many "coincidences" for my taste.
The only good thing I could find about the anime is that the main characters are hot guys, which is such a waste really. I would not recommend watching Weiss Kreuz unless you find yourself totally bored with absolutely nothing better to watch.