Souka was born into the Tsukihime family, landlords of the entire region descended from a house of samurai. Living in a temple deep in the mountains of Nagano, they are known as the "mountain kings" with a bearing greater than that of the Tohno household. Raised in such an environment, Souka rebelled and developed an interest in rock music. She came to be roommates with Akiha and Hanei at the Academy, and made plans to live together with Hanei and attend college after graduating from high school.
While she outwardly appears be a petite, charming young girl, Akiha claims that she has the personality of a handsome man. Rather than being a "girl that's cool like a man", she is more of a "stylish girl." With a masculine laugh and incredibly stern speech, she always tries to be as succinct as possible. She prefers not to wear her school uniform outside of her studies, and changes into casual clothing that leaves others believing her to be a boy at first sight. Her response to her upbringing caused her to develop her tastes into an entirely different direction. The simple fact that she wears such clothing despite that is enough to show the severity of her rebellious spirit. She is an unparalleled lover of rock music, and she becomes stressed at her family's lack of understanding of it. She sneaks away from the dorms at least once a week to partake in live shows at clubs.
Akiha describes her as someone competing for first or second most unique amongst the students. Despite her demeanor, she is actually extremely caring. She is very close to Hanei, looking out for her due to her easygoing personality. As she is so insistent despite Hanei's complaints, she is said to have the second coldest heart in the dorm. While considered to be a "lopsided pair" with the larger Hanei, the students consider them to be a "match made in heaven" and the "school's best couple", although Souka vehemently denies it. She views Akiha as her mentor, though she is both blunt and teasing with her. She is the balance between her roommates, and considered to be secretly popular as a "reliable but hard to talk to student" in the dorms. She is also close to Akira Seo, considering herself to be Seo's protector, and they often go to concerts together.
During the main story, Shiki Tohno encounters Souka during his time with Akira. One scene features them meeting as Souka is waiting to meet up with Akira for a concert. Shiki believes her to be a boy, and she acts very protective of Akira around him before leaving.
During another scene, both Akira and Souka plan to meet at lunch, but Akira gets sidetracked with Shiki while Souka has other business. They meet afterward at three, and Shiki again believes Souka to be a boy. Souka is hostile to Shiki, mentioning that a high school student being around a middle school student is unsightly. While Akira defends Shiki, Souka teases her about flirting with him. This causes Akira to fear the possibility of retribution from Akiha, and Souka reminisces about the events on the roof of "A Story For the Evening." Still continuing to tease Akira, she tells Shiki not to "step over the boundary" with her even if he thinks she is cute. Given that Akiha likes Akira, him meddling would make the situation a mess.
During "A Story For the Evening", she returns to the academy, and while depressed, notes that Akiha's pains, set after losing Shiki in her route, are much worse than her own. After Tsukasa Shijyou asks Akiha for advice about wishing away someone with a curse, she tell Akiha the first person that Tsukasa would seek out after regretting her actions would be the person she cursed.
While originally meant to appear in Tsukihime and even having sprites prepared for her, she did not appear in the story at all.
 Tsukihime Dokuhon PlusPeriod - TSUKIHIME Dictionary: Souka Tsukihime [Person's name], p.184
Plus Period | Tsukihime Data Collection
Souka Tsukihime [Person's name]
A student enrolled at the Asagami Academy for Girls. Akiha is her roommate and mentor. Her tone of speech is incredibly stern, and she always tries to be as succinct as possible.
Her outward appearance is that of a petite, charming young girl, but according to Akiha she has the personality of a handsome man.
An unparalleled lover of rock music, she slips out of the dorms at least once a week to go to live shows at clubs.
However, she's not a girl that's cool like a man, she's just a stylish girl.
She appears in Kagetsu Tohya, where she is the balance between her two roommates, Akiha and Hanepin. In the dorms she is secretly popular as a reliable but hard to talk to student, and despite her demeanor she is actually extremely caring.
Her parents' home is a temple deep in the mountains of Nagano. As landlords of the entire region, they are also known as the "mountain kings". Her love of rock music can be considered a form of rebellion against her family.
After graduating from high school, she plans to attend college while living together with Hanepin.
 Tsukihime Dokuhon PlusPeriod - TSUKIHIME Dictionary: Misawa Hanei [Person's name], p.189
Hanei Misawa [Person's name]
A first-year student at the Asagami Academy for Girls, and one of Akiha's roommates. Her nickname is Hanepin.
She has an easygoing personality, and is pretty large for a girl. This makes her something of a lopsided pair with the petite Souka, but according to all the other students they're a match made in heaven. Though Souka herself vehemently denies it, it seems that it's generally acknowledged that she and Hanepin are the school's best couple.
She is absolutely hopeless when it comes to keeping things tidy and in order, and her personal effects are always spilling over onto Akiha and Souka's desks. But even so, her dexterous fingers and scrupulous nature allow her to excel at crafting small goods. She receives countless requests from both students and teachers, which she inevitably accepts without hesitation. Because of this, she always seems to be busily working on some thing or another.
She appears in the Kagetsu Tohya side story "A Story For the Evening". She is the most therapeutic character in all of Type-Moon, and has a huge number of hidden fans. Also, this is supposed to be a secret, but it seems she actually has the largest breasts out of all the girls in Tsukihime.
- Kagetsu Tohya - a day - Streets - Afternoon - Akira-chan and the mysterious boy in the park
- Kagetsu Tohya - Ten Nights of Dream - A Story for the Evening