Akutagawa Ryunosuke (Mermaid au)

Akutagawa is a mermaid of ancient origin. He has a black-and-white idea that the strongest survives in this world. he is prone to violence. he is not afraid of pain and defeat. he believes that the one who kills another person deserves to live. But Atsushi behaves more gently, trying not to offend him.

It has a red-purple tail, with many scales and two additional fins near the hips. There are gills on the neck, and there are also some scales on the shoulders. His eyes are gray, his hair is black with a disheveled haircut and two white strands on both sides.

Extra:
Akutagawa is in love with Atsushi , but hides it and denies it
Akutagawa is very old , but by human standards, 20 years old
At night, he makes whale sounds to calm Atsushi down after work.
Sometimes, in Atsushi's absence, he looks at the photos with him on the wall in his room