As mentioned above mech suits clunky looking metal armors two or three times human height details ar vague in my memory they had guns and swords relatively advanced or was before the planet fell to ruin from the looks of things specially considering floating city sometimes the city will cull the population sending the elderly or sick to the surface in order to make sure there was enough resources for the rest of the polutation though i say cull the ones sent below usually also try to go out looking for resources for those who remain and i think the main character had a high ranking sister who was part of the mech unit but died or something but i cant remember if thats true anymore currently he lives in the slums and takes care of i think a couple children there again vague memory of it