Kohaku

Kohaku is one of the five main heroines of Tsukihime alongside Arcueid Brunestud, Ciel, Akiha Tohno, and her sister Hisui. Her character image song is Yarawaka na Kizuato, sung by Cocco.

She is the older of the two twin maids in the Tohno mansion. Her name, Kohaku, is the Japanese word for amber, referring to her eye color.

Background
Kohaku was originally a member of a branch family of the Fujou clan, but was brought with her sister Hisui to live in the Tohno mansion, because the Fujou clan had a special power of giving others energy. Makihisa Tohno needed this ability in order to keep control of his body. This transfer of energy is strongest though the means of sexual intercourse.

Due to this, she, as a child, was constantly raped by Makihisa, and unlike the other children, she had to watch them from afar as they played together. Just before Shiki leaves the mansion to live with the Arima family, Kohaku gives him her favorite ribbon and makes him promise to return it, indirectly begging for him to return.

Some time later, Makihisa decided to give more freedom to Kohaku, but in order to do it, she had to take care of an imprisoned SHIKI (who was imprisoned due to the Shiki incident and the fact Makihisa did not want to kill his son). However, some time later, due to having to keep control of his body, just like his father; SHIKI raped Kohaku. This drove her further into despair and decided to get revenge on the Tohno family. To do it, she twisted and brainwashed SHIKI with her medicinal herbs, all for the sake of her revenge. Some time later, Akiha and Hisui learned of Makihisa's sin against Kohaku, and it depressed them greatly. Akiha freed Kohaku from Makihisa and she became a normal servant. But Hisui was still depressed so Kohaku, seeing her sister's free enthusiasm falter for her sake, promises Hisui that she will "take on her role" until she was cheerful again. Ironically, it is because of those words that Hisui is unable to return to her old self.

Due to her intervention, SHIKI killed Makihisa, which was the reason why Shiki returned to the Tohno mansion.