Kamigawa Hiyori manages to walk the fine line between tolerable and insufferable. She can be unbelievably arrogant and condescending, not to mention smug beyond-all-reason, but she still manages to find some space for compassion and respect that tempers her less agreeable traits to some degree.

She grew up in a household that put insane expectations on her shoulders which spurred her development and allowed her to become quite talented. As one would expect of someone exposed to the internet for most of their life - and practically lived in it - she developed some less appealing traits. Hiyori is as much of a little gremlin online as she is in person.

Since joining U.A. she has become a little more tolerable. She's easy enough to get along with so long as whatever she is expected to be doing doesn't involve a lot of physical work or going outside. Not that she's out of shape or anything, she has actually kept in pretty good physical condition for a shut-in, mostly so she can play VR games without issue, but Hiyori isn't keen on being removed from her technology so she's prone to carrying at least a tablet with her.

As Hiiro Kurumi, she plays the role of Vampire Queen and Demon Lord rather well, and her slightly toxic, overbearing, and tremendously smug attitude fits the character a little too nicely.

Hiyori grew up in a household without a father, as he died in the line of duty as a hero. Her mother, who was suspiciously overbearing, put a ton of pressure on her to grow and perform. Hiyori lived and breathed technology, and her quirk was perfectly designed for it, too. Though it wasn't quite what her mother wanted, as she'd probably have preferred she had a quirk she could influence the growth of, it was a very promising one that sufficed.

To say that it impacted her development would be an understatement. She didn't get out much, she didn't really have a chance to make friends, and her mother treated her like a show piece for her friends and in front of her peers. It drove people away and it forced Hiyori to be self-sufficient, or at least, happy on her own.

It didn't bode well for her social development, and she was on the verge of becoming a true-blooded NEET - a regular drain on society! However, Hiyori took it a few steps further and turned her quirk and her tech savvy towards darkness. Around the age of twelve she became a bit of an online menace as a hacker, but her antics didn't last for long.

Despite numerous high-profile shenanigans, the long-due consequences of her actions caught up to her. Hiyori ran afoul of the law and got into a whole host of trouble, but it may have been the turning point for her, because instead of being clapped in irons and deposited into a jail like an adult might have, she was treated with some leniency. However, she had to do a bit (a lot) of community service, and so began her career as a white hat hacker for the Japanese government.

Even though she lacked some experience compared to more veteran specialists, most hackers didn't come equipped to literally become a supercomputer, and so it didn't take long for the name Gatekeeper to start circulating. Was the Gatekeeper some sort of secret super AI built by the Japanese government or a team of hackers that exceeded all expectations? Neither! It was some smug little gremlin in a closet somewhere in Tokyo! So long as she was on the clock and watching, breaking in where someone didn't belong proved to be far more difficult than ever before.

Hiyori's life was still a bit rocky. She didn't like to go outside and beyond attending high school rarely interacted with other people directly. The only saving grace was that she decided to step into the world of Vtubers and created an online persona for herself by the name of Hiiro Kurumi. As the pint-sized vampirette, she took to the gaming world at night and began developing a small but loyal following than enjoyed watching a cute, smug vampire girl kick butt in their favorite games. One or two may have submitted several requests for her to step on them in exchange for a rather large sum of money, but that information stayed private - mostly...

But it was soon not enough for Hiyori who really wanted even more out of life. Her quirk was strong, or at least she felt that it could be, but she had no idea how to really make use of it. So, she took the plunge and applied to U.A. Hero Academy. It was not a move that anyone who knew her expected, and she may not have, either!

She applied as a hero, and so she took the entrance exam like any other. Fortunately, despite being woefully underwhelming in anything related to physical practicality, her quirk excelled in its field! She managed to survive and impress at least one person.

It was a sufficient enough display to get her admitted. However, she also decided she wasn't too keen on the whole physical danger thing, so she changed her mind and applied for the support course where she could build things instead.

Now, as part of U.A., she has set up her equipment in her dorm and spends most of her time there when she is not in class or doing something necessary.

Mainframe is the quirk gives Hiyori the ability to link with technology and to create new technology, some of which will only work for her. In many ways, she is a human A.I. - or at least what many people perceive a highly advanced A.I. to be capable of.

She can directly connect herself to technology via the creation of a number of large, fiberoptic cables that spawn from ports all across her back. Once interfaced with technology, she becomes technology. She can control it with her mind, see what she needs to see, and do what she wants to do - and because she can do so in such a fashion, Hiyori is more capable with technology than even a full team of specialists.

Mainframe has converted part of Hiyori, specifically her heart, into a potent power generator she calls the Dynamo. It functions in place of a normal heart, and replaces her blood with nanomachines that pair with her cables, all of which is shielded from basic EMPs. By using these nanomachines, she can use her cables like a 3D printer to create any technology or device she can think of, even if it normally shouldn't exist.

Hiyori's brain is also infused with nanomachines and advanced technology generated by her quirk that gives her an incredible perception and information processing needed to "become the machine". Without it, controlling an army of drones would be impossible.

Though Mainframe is a very powerful tool for interfacing with technology, it only helps if technology is available. She must be able to directly interface with something, and can only then access technology if it is connected to it wirelessly or otherwise - so she cannot access closed systems.

Once Hiyori spawns her cables, which can easily overtake a small room if she gets out of hand, she loses almost all of her mobility and generally has to stay put. She can disconnect them on the fly by shedding them, but if it has come to that she's in trouble.

Hiyori's quirk requires a lot of mental power. Her brain is enhanced and extremely advanced, but the more "multi-threading" she has to do, the faster she runs out of energy. Controlling a bunch of drones while simultaneously hacking into and controlling surveillance systems across the city will wear her down real quick.

While Hiyori can create technology with her quirk, she has to know how to do so if she wants others to be able to use it. Therefore, she can create permanent, usable technology for others if she studies and prepares. If she creates something with her quirk that normally wouldn't exist, such as a raygun or stunner or some other such piece, it will only function for her, as the Dynamo powers it.

Hiyori's quirk is exceptional for technology, and if she didn't have the know-how to make it work, then it wouldn't! Fortunately, Hiyori is a genius when it comes to technology - even mundane tech that she didn't create. However, she still has a long way to go in mastering the craft, but its likely only a matter of time until she does.

She is quite handy when it comes to crafting, and even though she can use her quirk to assist, she doesn't have to. She can go about it the old fashioned way if she absolutely has to.