Kaijuu Sekai Seifuku

Four tiny, dragon-like monsters arrive on Earth with an ambitious goal: world conquest. Their grand strategy immediately stalls when they move into the apartment of an ordinary office worker in her twenties and decide that understanding humanity should come first. Between freeloading, household chores, snacks, and microscopic preparations for domination, their secret base becomes less like a villain's lair and more like an extremely strange shared home.