In the Attack on Titan universe, Eldians are an oppressed group of ethnic minorities. In the country of Marley, they are forced to live in internment zones and are treated as second class citizens without any civil liberties and regularly suffer abuse from Marleyan police and civilians.
"Warriors" are Eldian children who volunteer to join the Marleyean military to become Titans, extremely powerful humanoid weapons. Warriors participate in very dangerous missions, often against foreign Eldians, and have a maximum lifespan of 13 years. However, Warriors and their family members, including future generations, automatically receive honourary Marleyan citizenship and gain the rights of regular Marleyan citizens.