Earthian

Chihaya, an angel with black wings, is a plus checker from the planet Eden who travels to Earth with Kagetsuya, a minus checker. Together, they monitor Earth events as part of a centuries-long observation, keeping track of a score that can determine the planet's fate. If the score dips below minus 10,000, Earth will be destroyed. Chihaya and Kagetsuya's experiences among the human inhabitants, known as Earthians, unfold as they navigate their duties.