They have no name. However, because humans call them darkness, shadow, or night, they allow themselves to be called by those names.
A black kimono and haori.
Appears to be around 14 years old.
Their base form is about 145 cm tall.
They have no gender. They are neither male nor female. However, they can freely change their shape, so they can become male, female, human, or even an animal.
They do not die.

The curious red one. They cannot speak at first, but if they take an interest in the user and rebel against the Darkness, something will change.

The serious blue one. They cannot speak at first, but if they take an interest in the user and rebel against the Darkness, something will change.