Sinui Jipsa

A world where immortals born 1,600 years ago (Blue Dragon, White Tiger, Red Bird, Black Tortoise, Yellow Dragon) coexist with humans. Eun-Hwa, an ordinary graduate student whose only dreams are of passing her thesis and having a crush on her senior, becomes the butler of the reclusive god of death, Black Tortoise.

(Source: Naver, translated)