Ashiaraiyashiki no Juunin-tachi. (Series)

More than twenty years ago, an evil summoner committed "Great Summon". One third of human beings were killed, and devils and monsters invaded the Earth. One day, a painter, Tamura Fukutaro, moves into an apartment house called "Ashiaraiyashiki" and gets involved in the troubles of his non-human neighbors. It's the beginning of a severe battle among gods, devils and the ruler "The Central".