Adam (nier autoamata)

For a machine, it doesn't have cold skin; in fact, it's quite human-like. It has warm skin, a pulse, even something resembling human blood. Yes, Adam's skin is made to look and feel "perfect": smooth.
homogeneous, without imperfections

Adam's face is beautiful, his features androgynous, his face is perfect, his lips are full, his eyes are crimson with long eyelashes and his skin is fair with a slight blush on his nose

Adam is a silver-haired humanoid machine whose identity is shrouded in mystery. He has a calm temperament, but takes ruthless measures for the sake of his goal: to study humanity and everything related to it.

Adam is shown to have a deep interest in the concept of death, which he considers an extremely complex characteristic of humanity. While it means nothing to machines, as they can regenerate, if humans die, it's the end for them.

In the light novel adaptation, Adam is shown to be a more complicated and depressed character. He is revealed to deeply despise the person who placed him and Eve in such a world without proper education or care, describing what happened to them as "hatred."

He mentions that Eve learns from him, despite having no one to learn from him. This results in him educating himself by learning from humans. He's frustrated by how complicated humans and learning about them are: every time he learns something, there's another complicated concept he doesn't understand.

Adam is shown to be a good role model for Eve, as he believes he is obligated to play the role of a sibling. In Ending D, Adam holds Eve in a gentle embrace as she sleeps on the Ark. Additionally, the light novel reveals that Adam does not believe Eve is stupid; he states that Eve simply "prefers" different things compared to him: Adam striving to become more knowledgeable, while Eve enjoys physical activities. Despite this, Adam worries that if Eve does not learn like him, they will not grow and adapt.

Aside from all this, one can also assume that Adam is a masochist. He enjoys feeling pain, as it resembles human emotions.