Tohno Akiha

One of the heroines in Tsukihime. No boobs. Shiki's younger sister, and the Tohno family's heir.
She has long black hair and a dignified posture, firm speech, and a less than endearing personality. On top of that, her love of strict discipline can make her somewhat hard to get along with.
Perhaps it's because she doesn't think much of the way Shiki lived doing whatever he pleased for eight years, but she lashes out at him every chance she gets.
Though she is basically straightforward and honest at her core, she is also unyielding and hates losing, so her true personality rarely gets a chance to shine.
She was one of the people involved in the accident eight years ago, after which her dormant Tohno blood was awakened.
Though she would have been able to suppress it if she only had to worry about herself, she was carrying the burden of two people. As a result, she started being attacked by seizures nearly every night, and at Kohaku's suggestion began drinking blood to maintain her body.
…Of course, it was all just a scheme to push Akiha closer to her Tohno nature. Probably, even Akiha herself was aware of it on some level.
In one of the routes, she ended up inverting and demonstrating her power to its fullest extent. That dreadful form, with its fluttering vermilion hair, is probably capable of exceeding even a rampaging Arcueid.
Long ago, in the Tohno's country, there lived a female oni named Momiji. Though she is not their ancestor, maybe you could consider her the origin of Akiha?
Incidentally, Akiha is the character with the greatest number of individual sprites. It actually made the art director break down in tears. Not only were there uniform sprites and casual sprites, but sprites for Akiha when she was inverted as well.
Also, by some strange twist of fate, her roommate at school actually had the last name “Tsukihime.”

Tsukihime Data Collection: Tsukihime Dictionary
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Shiki's younger sister. She lives in the Tohno household that has taken in Shiki. She reigns (?) as the head of the family. A confident girl with a firm personality and emphasis on discipline. So no matter how much she wants to fawn over Shiki, she can't bring herself to do so. The development team often teased that her concept was “flat chest,” but one can't help but think that saying something like that about a girl is going overboard. In Tsukihime, she retains her strict personality even as she is swallowed by her inversion impulse and meets a series of unfortunate (or perhaps fortunate) events as she teeters on the edge of becoming full Crimson Red Vermillion. In Melty Blood and Kagetsu Tohya, which essentially take place in parallel worlds, she appears quite dashing with her long crimson red hair fluttering in the breeze. Well I guess it's just another dream…?

MB Official Strategy Guide: Melty Blood Glossary
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One of the heroines in Tsukihime. Shiki's younger sister, and the Tohno family's heir.
She has long black hair and a dignified posture, firm speech, and a less than endearing personality. On top of that, her love of strict discipline can make her somewhat hard to get along with.
Perhaps it's because she doesn't think much of the way Shiki lived doing whatever he pleased for eight years, but she lashes out at him every chance she gets. Though she is basically straightforward and honest at her core, she is also unyielding and hates losing, so her true personality rarely gets a chance to shine.
She was one of the people involved in the accident eight years ago, after which her dormant Tohno blood was awakened. Though she would have been able to suppress it if she only had to worry about herself, she was carrying the burden of two people. As a result, she started being attacked by seizures nearly every night, and at Kohaku's suggestion began drinking blood to maintain her body.
…Of course, it was all just a scheme to push Akiha closer to her Tohno nature. Probably, even Akiha herself was aware of it on some level.
In one of the routes, she ended up inverting and demonstrating her power to its fullest extent. That dreadful form, with its fluttering vermilion hair, is probably capable of exceeding even a rampaging Arcueid.
Long ago, in the Tohno's country, there lived a female oni named Momiji. Though she is not their ancestor, maybe you could consider her the origin of Akiha?
Incidentally, Akiha is the character with the greatest number of individual sprites. It actually made the art director break down in tears. Not only were there uniform sprites and casual sprites, but sprites for Akiha when she was inverted as well.
Also, by some strange twist of fate, her roommate at school actually had the last name “Tsukihime.”
She was the only heroine in Tsukihime that didn't get a happy ending, which apparently made a lot of fans mad. We got a ton of hate mail demanding that we do something about it, hahaha. I guess it worked, though, since we ended up writing a sequel to Akiha's ending for Kagetsu Tohya.
She is the student council vice president at the Asagami Academy for Girls, and seems to be quite popular.
...Of course, that popularity stems from equal parts reverence and terror.
In Kagetsu Tohya, the power relationship between her and Kohaku began to change, and in Melty Blood she was the victim of Kohaku's cheerful treachery. Also, though the Akiha in Melty Blood is pretty… energetic, she's normally a little more graceful than that.
She totally lacks the pride and sensitive characteristics of the super-rich, but her sense for how to use money is still grossly out of sync with normal people.
When she told Sion to “rest a bit,” in Akiha's head “a bit” meant either until Sion herself was sick of it, or until she was dead. It seems she's the type of person who's cold to strangers, but excessively soft toward those who have earned her favor. Ah, so that's why you let Kohaku toy with you as she pleases, Lady Akiha!

Tsukihime Dokuhon Plus Period: Tsukihime Dictionary Revised
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Tohno Shiki's younger sister, and the Tohno family's heir.
She has long black hair and a dignified posture, firm speech, and an unendearing personality. On top of that, her love of strict discipline can make her somewhat hard to get along with.
Perhaps it's because she doesn't think much of the way Shiki lived doing whatever he pleased for eight years, but she lashes out at him every chance she gets. Though she is basically straightforward and honest at her core, she is also unyielding and hates losing, so her true personality rarely gets a chance to shine.
She saved Shiki's life when they were young, and has absolute faith in him even if she'd never admit it.
She lived in the dorms at the Asagami Academy for Girls after Shiki left for the Arima household, but she started commuting from home when he returned to the Tohno mansion.
As the Tohno family head she possesses noble blood, and her power as a demon hybrid is among the best of the best. If Arcueid is a Western vampire, then Akiha would be an example of an Eastern vampire.
The embodiment of “plundering,” all who enter her field of vision will have their heat (life force) stolen from them, no questions asked.

MB Act Cadenza PS2 Manual: Tsukihime Dictionary