Tohno Makihisa

Akiha and SHIKI's father. The person who took in Kohaku and Hisui, and adopted Shiki.
A mischievous prankster who has diligently protected his private papers.

Tsukihime Data Collection: Tsukihime Dictionary
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Akiha and SHIKI's father. He took in Kohaku and Hisui as tools to restrain his Tohno blood, and adopted Shiki for his own amusement. He was a mischievous prankster who has diligently protected his private papers. He has a strong, self-indulgent feeling of being victimized, and you could probably say that it was this weakness that invited tragedy into the Tohno family.
In order to protect his family (blood relatives) and solidify the Tohno's position he forged connections with the demon hunter organization, which was locked in a cold war with the demon hybrids at the time. By entering into a cooperative relationship with the demon hunters, he was able to gain sovereignty over the entire Misaki City region.
However, he was still unable to control his dread toward Nanaya Kiri, the bloodthirsty killer he saw as a youth while serving under a certain old man. So, after consolidating his power, he launched a surprise attack on the Nanaya village and completely wiped them out.
As for how he died, that was covered in the main story. It was karmic retribution, an end appropriate for one who was in no way a bad person, yet caused so much harm.

Tsukihime Dokuhon Plus Period: Tsukihime Dictionary Revised
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Father of Tohno Akiha and Tohno Shiki.
Akiha becoming the family head after his death is what kick-started the story of Tsukihime. At that time, she called back the disinherited Shiki to the Tohno mansion, and restarted their brother-sister relationship where it had left off eight years ago.

MB Act Cadenza PS2 Manual: Tsukihime Dictionary