"Sample D" is a batch of artificial humans. They were raised as human weapons for "Bio" country.
On the outside, they looked like ageless 14-year-old boys. They don't understand human love because they were never taught such thing.
When the "Bio" country and the "Neo" country engaged in combat, "Sample D" was deployed to attack "Neo". This resulted in countless civilian casualties for "Neo".
After the defeat of "Bio", "Neo" government condemned "Sample D" and tortured them for revenge.
"Sample D" didn't understand love between humans but they protected their members. Stronger members of "Sample D" would volunteer to be tortured for the weaker members.
Under the harsh treatment, "Sample D" died out until there were only 11 left. These 11 were malnourished. They were so thin and weak, only skin and bone.
At that moment, the 7th prince of "Neo" decided that the torment of "Sample D" was enough. He asked his brother, the king, to relinquish the group to his command.
The 16-year-old 7th prince, a war hero of the Bio-Neo war, knew very well the crime of "Sample D", but he also knew it was worthless to keep torturing them. He wanted "Sample D" to do something more useful for "Neo". He put "Sample D" under his watch, fed them, healed them.
When they were stronger, he and them began rebuilding the destroyed houses, bridges, buildings caused by war. Gradually, the surviving leader of "Sample D" grew to like the prince.