Earthian

Chihaya, an angel, and Kagetsuya, a fellow angel, form a pair of checkers tasked with monitoring human activity on Earth. Their mission involves tracking significant events as plus and minus checkers, with the goal of preventing a catastrophic outcome: if their score reaches a deficit of 10,000, Earth's existence will be at risk. Chihaya, an anomaly with black hair and wings, joins Kagetsuya on this assignment, and their observations lead to interactions with various humans.