"Welcome to my home! Enter freely. Go safely, and leave something of the happiness you bring! ... I am Dracula; and I bid you welcome."
- Dracula, Chapter 2
Yu~ki's character is based off of Dracula, or Vlad III the Impaler - though clearly off the former more than the latter. In his youth, Yu~ki studied the black arts at the academy of Scholomance in the Carpathian Mountains, which overlooks the town of Sibiu (also known as Hermannstadt). An avid scholar, he became proficient in alchemy and the art of magic and once satisfied with his schooling, took on a military career and combated the Turks across the Danube.
He must indeed have been that Voivode Dracula who won his name against the Turk, over the great river on the very frontier of Turkey-land. If it be so, then was he no common man: for in that time, and for centuries after, he was spoken of as the cleverest and the most cunning, as well as the bravest of the sons of the 'land beyond the forest'.
- Dracula, Chapter 18
Yu~ki here seems to deviate from standard Dracula fare - he meets and falls in love with Cecilia, and the young Transylvanian nobleman married her young at the top of his military career. Their happiness was brief, however - Cecilia became sick and died young, before they had even one child. Distraught and disenchanted with life, Yu~ki turned even further into the world of alchemy and magic. He lived a long life alone in his castle in the Carpathian Mountains near the Borgo Pass. Once he died, his work in the black arts allowed him to come back as a vampire - now to live eternity with his mourning.
As years wore on he grew in strength and notoriety - few knew of his real abilities, however. At one point in the wearing on years the man Közi came to him - knowledgeable in the black arts and in want to be changed into a vampire, pledging his service to Yu~ki. However, once the deed was done it eventually became clear that something went wrong - Közi was already bound to Mana, and as such the service bound to Yu~ki was now Mana's. Yu~ki and Közi were quite close nonetheless, and for some years all was well - Yu~ki could even forget some of his pain. However, as years wore on and Közi strengthened, he began to distrust Yu~ki and think him evil - Mana's submission to him did not help matters, either. At the same time, Yu~ki began to suspect that Közi knew all along that the deal would turn out as it had.
The Earl of Dracula did not like to be fooled.
There was a falling out, though there was little violence - Mana and Közi then were staying in England, while Yu~ki remained in Transylvania.
During the next years Yu~ki took on brides that he changed to be like him - but his vampire brides could do nothing for his heart, and while he loved them all it was a fleeting emotion that fled him quickly. As the years went on the emotions other than sorrow and anger faded, and he eventually decided to go to England - though whether for simple change or for more nefarious reasons is never made clear. Jonathan Harker (Klaha) was the man chosen to aid him in his move, and was welcomed into the Earl's home. During his stay however, Yu~ki spots the picture of Klaha's betrothed in the locket around his neck - a perfect match to the portrait of his deceased wife. When he finds her name is Cecilia, it is even more apparent.
Yu~ki was convinced that this Cecilia was one and the same as his own beloved, and the cunning vampire would stop at nothing to return her to his arms - for, while increasingly unkind under the surface as years wore on, the romance and love in Yu~ki for his Cecilia would never fade. After hatching a plan, he let loose his brides on Klaha and fled - to London, and to Cecilia.
"Yes, I too can love. You yourselves can tell it from the past. Is it not so? Well, now I promise you that when I am done with him you shall kiss him at your will."
- Dracula, Chapter 3
The Earl had already been affecting Cecilia before he arrived - she had been dreaming of him, and confessed to a nun - who told her simply to pray about it. This nun is of course Mana - who was still indebted to Yu~ki. Mana visited Cecilia in the dead of night, to find Közi there attempting to drink from her. Mana stopped him and informed him that Cecilia was the Earl's virgin bride - another step up in the jealousy that Közi felt, now with further knowledge of Mana's continued servitude.
When the Earl did arrive in London, he met Cecilia 'accidentally' and gave her the locket he had taken from Klaha. While Klaha was still incapacitated by his brides, he took to the task of changing Cecilia to be his own. By the time Klaha manages to return, Cecilia is 'ill' and bound to her bed covered with a cross - a priest tried to exorcise her, but the Earl appeared and instead killed the priest and set Cecilia free. It was clear now that Cecilia was a vampire - the Earl took her then and disappeared.
The next time the Earl appeared was after Közi informed Klaha that he needed to kill Yu~ki to set Cecilia free - and after the long travel to Yu~ki's castle, Mana, Cecilia and Yu~ki are all found there. Közi and Yu~ki fight - Közi managed to greatly wound both Mana and Yu~ki before being defeated - which marked the end of the Earl's long life and afterlife.