Gunslinger Girl (2003) IMDb
Italy. A secret government organization, apparently designed to deal with terrorism and the mafia, reconstructs little girls who are seriously injured. The children are mechanized and their minds are harshly conditioned. They look like ordinary innocent kids, approximately ten years old, but are competent assassins and bulletproof killing machines, dead to normal society. Each one is paired up with an adult agent. To remain loyal, the children’s minds are engineered to produce feelings of affection for these agents, many of whom treat the little soldiers as something inhuman.
Tragic action. Children with guns and issues. Severe realism saves the very peculiar concept.
References here: Hinamatsuri (2018).