His name and its meaning: Kohaku is the japanese term for the gemstone "amber".
Nature: "Low ranking" Angel , still very young and learning from Hisui, his friend, one of the Archangels.
Appearance: Slender, fairly fragile-looking (though not by far as thin as many other Clamp-characters such as Kamui or Subaru). Kohaku has blonde, fine hair which is longer on one side, and rather short on the other. He has large, innocent-looking eyes (large eyes=>symbolism for young innocence) and usually wears gown-like clothing which slightly resembles Belldandy of "Ah Megami-Sama" 's outfit.
Age: Since Kohaku is an angel, he has no specific age. However, he counts among the young and inexperienced angels who have yet to learn from the older Archangels.
Abilities: His "Hougan" (the term for magic used in Wish) is that of being able to Heal and support the young angels as they hatch out of the "eggs" by singing. His singing also seems to have large effect on nature and animals in general. Kohaku's destructive/defensive magic is still very underdeveloped.
Dislikes:Eating meat (in fact, he actually isn't allowed to consume it at all,since it is a sin to angels to eat anything made out of dead animals), Being picked on by Kouryuu and Accepting favors.
Enjoys: Nature and communicating with its inhabitants, Going for walks, Being around Shuichiro and Hisui, Helping people.
Favorite Food:Being an angel, Kohaku solely drinks milk and is not allowed to consume anything made out of animals.(meat) All angels need in order to survive is sunlight, which nurishes them.
Random Facts:
Kohaku, like all angels of "minor importance", turns into a small version of himself during nighttime, due to the lack of sunlight. This is shown by making Kohaku look like a SD (super-deformed; chibi)-type figure in the manga. Having this appearance, his magic becomes less effective and he is overall a lot weaker.

Kohaku is resposible for the birth of the new-born angels in heaven. He is able to make them hatch from their "eggs" by singing.

He is able to "summon" a water spirit, which he often makes use of when watering the garden in order to help Shuichiro.

He is able to sense another angel's "light" by concentrating on the surroundings. This "light" which emits from every inhabitant of heaven comes from its wings.