Stone Flower

Ruten, a sick young girl living alone in a massive house in Kyoto, hires a woman named Kana to be her live-in housekeeper after a disastrous interview turns into a possible friendship. Kana is no ordinary woman, however—and nor is the Kyoto that she and Ruten live in, or the situations they find themselves in. Why is Kana immortal? What happened to cause Kyoto to be shrouded in a black mist for the past millennium? Why are there reptile people everywhere outside the city?

(Source: MangaDex)