Is Earthian coming back?

Angels from the planet Eden have been watching Earthians, the inhabitants of Earth, for 5 billion years. Chihaya, an angel with unlucky black hair and wings, is a plus checker who travels to Earth with Kagetsuya, a minus checker. Each team of plus and minus checkers keep track of Earth events and, if the score ever reaches minus 10,000, the Earth will be destroyed. The story follows Chihaya and Kagetsuya and the different people and events they observe on Earth.