We've looked at some pretty weird things that have been done in Japanese media. "Gunslinger Girl" isn't a freak fest like say Kekko Kamen. If anything the series is very understated. So it slinks down from weird to creepy. The plot is simple, in Italy a faction of the government has created high tech assassins. To make these assassins they find little girls who are orphaned and sick and give them new bodies, and brain washing, and guns. They are then assigned to adult agents that act something of leash holder/big brother. Its just really creepy watching these girls being given the illusion of hope just to be squashed later on. Even the beginning credits give this feel with a moody song mixed with I would say inappropriate joy.