Tohru has naturally dark brown hair and eyes, which is typical of their Japanese descent. They currently wear their hair as a short bob, just above the shoulders, with bangs right at eye brow length.
Their skin is fairly pale, less due to any health complications, and more to do with the fact that they're slowly growing into being an indoor person, in comparison to the active child they used to be. Along with the paler skin, the early signs of bags have also begun to pop up, just a smudge beneath their eyes.
Regarding their build, they're rather soft and round due to lack of exercise, having no muscle beyond 'functioning'. They sit on the shorter side of average compared to their peers, but they still have hope their growth spurt hasn't stopped quite yet. It doesn't help that they're beginning to sport a bit of a slouch from the way they sit and lounge, curling in on themselves because "it's more comfy and less effort".
Fashion-wise, Tohru's still in the "I don't get it" and "being girly isn't fun" phase. While their friends start to talk about make-up and shopping, they'd much rather stick to oversized hoodies, leggings, and playing games. It's gonna take a bit for them to figure out it's not all that bad.

Tohru can be ascribed a few different words.
Some would say they're decently smart, referring to their good grades. While they aren't some genius, and studying is quite the bore, they haven't been struggling all too hard just yet.
Some would say they're rather shy or hard to approach. In class or in any social situation, Tohru generally keeps to themselves, keeping from joining any class discussions or speaking with people they don't know.
Adversely, some might say Tohru's pretty loud and excitable. If around people like family or friends, Tohru's quite the speaker, rambling on about their favorite series, asking random questions, or even just recounting random things from their day.
When speaking with Tohru, you might notice they're a little blunt, or honest if you want to be nice. While they can try to be sneaky when they want, they generally don't have the ability to lie outright, not having that on-the-spot thinking skills. While generally speaking, you can consider all the things Tohru says to be true, they also possess a bit of a dry deadpan humor that muddles the waters a bit. Despite this, Tohru thinks a lot about what others think or feel, constantly reflecting on how their words might have affected someone, or how their behavior reflects on them.
If Tohru ever deems you a 'good/chill’ person, they can be very loyal, sticking to only having 1 to 2 good friends rather than having a wide friend group. However, outside of those very few, Tohru can act a bit distant. While they get along with people just fine, they don't actively seek people out, only approaching people out of necessity or approaching them because it has been established that they don't mind Tohru's company. Depending on how you see it, you could call it cowardice, consideration, or being alert. As a result, while some people may find Tohru a fine person, they can also be rather forgettable, giving the impression of a loner or very selective.

Tohru was born in London into a Japanese household of half-blooded wizards, consisting of their mother Mitsuki, father Seiya, and sister Mashiro.

While both parents were born and raised in Japan, studying as students of Mahoutokoro, they had both (though in different years) experienced an exchange program with Hogwarts, temporarily experiencing Hogwarts and the British wizarding community. During their temporary enrollment, Mitsuki was sorted into Gryffindor, while Seiya was sorted into Ravenclaw.
Eventually, once both had returned and graduated Mahoutokoro, they had decided to move to London, either in pursuit of further education or professional opportunities. Eventually, both parents met, bonded over shared experiences, fell in love, all that shindig, resulting in the birth of Mashiro and, eventually, Tohru.

An interesting quirk of their family was their proximity to muggle culture. Both parents, in their own ways, had become interested in muggle culture, taking the time to learn about it on their own. When it finally came time to begin their own family, they had decided to live in a mixed culture neighborhood, teaching both children muggle and wizarding culture. The Asai family home was situated slightly off the more busy city, residing on the cusp of both muggle and wizarding communities. Growing up, both sisters were enrolled in an English muggle public school as general education, living with the strict house rule to only use Japanese and magic within the house. It helped to teach both children to naturally compartmentalize their cultures, both ethnic and magical. It also helped that children couldn't intentionally use magic until receiving their wands at 11, which at that point, they’d be enrolled in Hogwarts.

Mashiro, as Tohru's older sister, is 10 years older than them. Unlike Tohru, Mashiro was first born in Japan, only moving to the house they currently occupy at a young age. Unbeknownst to Tohru until very recently, Mashiro and Tohru were half-siblings, their mother having remarried to Seiya around the time of the move. Regardless, Mashiro treats Seiya like her father and vice versa. This information honestly had no effect on Tohru considering that it doesn't change the fact that Mashiro is their sister. Around the time Tohru was born, Mashiro had been enrolled into Hogwarts, having been sorted into Hufflepuff.

Due to some unfortunate circumstances regarding her health, Mitsuki, Tohru in tow, had temporarily moved to Japan for about a year and a half for treatment and hospitalization.

It was actually around this time Tohru was finally allowed to cut their hair to the short length it is now. They never really knew what to do with it, only ever tying it into a ponytail, but their mother wanted them to keep their longer hair for its feminine touch. But finally, after years of poorly maintained hairstyles, and the Japan heat, their mother agreed it would be more convenient to just cut it.

Both father and sister would visit whenever they could, but work and school made it impossible to simply relocate, especially when no one seemed to have expected it to take longer than a few months. It didn't sound all that serious of a disease, at least to Tohru's young ears. They had just thought the healers in Japan would fix her up, they'd enjoy Japan for a few months, and then they'd be back home. Unfortunately, treatment did not proceed as hoped. For a while things looked like it was going well, then complications had arisen, their mother's hospital room was moved from general wing to the protected wing, and then, one day after coming home from a day at Japanese muggle public school, Tohru was urgently taken to their mother’s bedside, along with the rest of the family, to say goodbye. Tohru's mother had passed away around a year before Tohru's enrollment.

Returning to London, Tohru was re-enrolled into their old primary school. While their friends welcomed them back, it seems the year-and-a-half time apart had allowed for time where both parties grew differently. While still close to their friends, Tohru had begun to drift a bit away, not able to follow in their conversations about fashion, gossip, or crushes. It almost felt like they had grown more mature while Tohru was away. It left a vague feeling of being left behind. When the letter from Hogwarts came, there was a sense of quiet acceptance that both them and their friends had changed, and well, that was okay.

To the months leading up to their enrollment, Tohru spent their days in a mix of excitement and anxiety, spending many a night staying up a tad too late on their new fancy phone (courtesy of finally reaching the age where their dad decided a phone would be a good idea) staying up a bit later than they pretend to sleep at. It's not like it helped really. You can't really search up information about Hogwarts for first years on muggle internet. It was just that, the idea of going someplace new, all alone without family nearby, living with a bunch of kids they don't know... it's terrifying. They don't even know if they can make any new friends, although they're quite accepting of the idea of spending a lonely, if not, peaceful school life. Despite all that, the thought of getting to FINALLY get their own wand, learn new magic, and feel a bit more grown up is just, well, brilliant. They're also rather excited about being sorted as well. Each of their family members have gone to different houses, and while Mashiro often joked that Tohru would end up in Ravenclaw since ‘vibes’ and that they're pretty similar to dad, the family had also joked a few times about completing the roster by having Tohru get sorted into Slytherin.
Overall, they're practically bursting at the seams with conflicting, but exciting, feelings.

When Tohru was 4 year old, their parents had decided to get a family dog. While she was a shy dog, keeping her distance from the family, she seemed to deem the small child as a non-threat, stalking them around the house.
Unfortunately for her, Tohru feared the new big (she was medium sized at best) black dog that would follow them around. One day, in a desperate attempt to put distance between them and the new dog, Tohru had accidentally magicked the front door open, which was far too tall for them to open or unlock. Tohru, not really understanding what they did, simply scampered out the door and slammed it close on the poor dog's face. Suffice to say, while their parents were happy that they reached a milestone, they were far more panicked to get their child back inside before accidentally running into oncoming traffic.

As a side note, let it be known, after a few weeks, Tohru and the family dog Nachi got along just fine.