Melanite

Melanite, formerly an experienced tester at a Columbian weapons testing company. Her contract with the company came to an end after she was infected with Oripathy. Thereafter, she came to Rhodes Island for medical treatment and entered into an agreement to become a field operator.

Imaging tests show the indistinct outlines of internal organs, obscured by abnormal shadows. Originium granules detected in the circulatory system. The subject is confirmed to be infected with Oripathy.

[Cell-Originium Assimilation] 6%
Operator Melanite's infection is currently still at an early stage; no Originium crystals can be seen on the body surface.

[Blood Originium-Crystal Density] 0.23u/L
Based on the patient's complaints and imaging evidence, it was confirmed that Melanite was infected via unusual means and mechanisms. Extra care is necessary during treatment.

Shortly after completing her examination and diagnosis at Medical, without talking to anyone else, the petite Phidia immediately headed to the HR office, set down a plain yet concise resume on the table, and simply said 'I'm applying.' After that, she sat down opposite the HR operator and simply stared without saying a word until the operator on duty was unable to cope with the pressure and ran from the room, claiming: 'This is above my paygrade. Show it to the higher-ups.'
Operator Melanite's quiet, indifferent, efficiency-minded, and aloof personality continued after her hiring. Although her employment test was repeatedly pushed back, on her first field mission soon after she took it, she was able to accurately lay fierce suppressive fire on the enemy's position immediately after being deployed on the battlefield. Almost singlehandedly, she made it so there was nothing for anyone else to do except cleanup.
Upon returning to Rhodes Island, the mission's captain treated everyone to a round of drinks. Naturally, Melanite was also invited. While everyone chit-chatted, teased each other, or argued, she simply sat there and sipped her drink. Some of the members thought she was perhaps being left out and tried to talk to her. Although her response was cold as always, she nonetheless engaged in some small talk until Midnight, who happened to be there, saw this.
At first, she simply kept quiet when confronted with his boastful attitude. This got those in attendance somewhat worried. Considering Midnight is known throughout Rhodes Island for the way he acts, they were all waiting to see how humiliated he would be in the end. It seemed Midnight must've said something wrong. Melanite started getting more and more nervous. In the end, she suddenly grabbed the railgun leaning against the counter and aimed straight at him.
Although this caused quite a ruckus, it seemed she did that only as a threat; she had no intention of actually shooting him. Afterwards, the two were both reprimanded and for a while had no interaction with one another.
Much, much later, the two of them ran into each other again at the bar. This time, Midnight treated her to a bottle of fine wine, while she gave him a bottle of perfume that she mixed herself, in addition to an apology.

I, too, bear some responsibility. To think I was blind to how guarded and tense you were... As someone who's made spreading happiness my life's mission, it was a major transgression on my part...
—Midnight

Faced with his boastfulness, Melanite once again found herself bewildered, but this time she didn't feel the insecurity she felt when she first reported in, nor did she mistake his attitude for sinister intentions.
Which is why she didn't pick up her railgun. Instead, she asked Spot, who was standing nearby, for his opinion, and ended up asking Midnight to join her on a one-to-one training session the next day.

[Promotional Material]
3. Prototype Single Unit Mass Projectile Lethal Weapon
One of the newest weapon concepts in the exhibition, and an innovation that will lead the Columbian weapons industry in a new direction...
...Extremely high kinetic energy and initial velocity, a trajectory that's nearly a straight line, and a complete equipment set featuring an AI assistant...
...It uses an ingenious new energy source to perfectly alleviate any weight concerns for use as a personal weapon...

[Classified Log]
Shit, man. Everyone at the company that made this railgun has got to be nuts.
They squeezed every kind of new technology they could into this shell! Right, they did use a module that uses minimal energy to maintain the highest initial velocity, and all the parameters are top-notch. And it's so light you could even carry it on your back. But did they ever stop to think about why no one else made a miniature version before they did? It's because technology isn't there yet. Who knows what's going to happen if this thing breaks down?
Right, and keep pushing back Melanite's employment test. Yes, indefinitely, until both Engineering and Medical are satisfied! It's crazy enough that this thing ever got made. But they even managed to find a weapons testing company that'd agree to have one of their employees bring this thing onto the field for testing! Forget testing. This thing is a ticking time bomb, even on standby. And once it's activated, it's practically guaranteed to have a measurable effect on nearby Originium activity! Most likely, this is how she got infected in the first place, and her condition's only going to get worse with each use—
What? You sure this is how she got infected? Does she know?
Know? Not only does she know, she's still not willing to let go of the gun!
Have her pay Engineering a visit. I need to have a chat with her.

Addendum: Based on Melanite's adamant personal request and her tendencies in battle—I'll cut to the chase. She's hiding it, but she's clearly afraid of not being able to provide us with the firepower support we need on field missions. She thinks we'd fire her over that, and no amount of explaining could convince her otherwise. In the end, we modified her railgun. Although its destructiveness has gone down, its impact is still nothing to scoff at. More importantly, after rigorous testing, it's now safer than ever.

Before she came to Rhodes Island, Melanite worked for a no-name weapons testing company. The company is small in scale, but its revenue is shockingly high—and there are many other similar companies. Put plainly, they are all companies that, aside from the industry juggernauts, the Columbian munitions industry needs to exist, no matter how grubby.
For example, Melanite's first mission at the company was to test a weapon of her own choosing, a seemingly very heavy crossbow. Her first fifteen days were spent on a short training course. On the sixteenth day, she brought the crossbow with her and joined her coworkers in suppressing the Rusthammers at a certain location.
The battle didn't last very long, as the Rusthammers were no match for the onslaught of the boosted crossbow bolts. As for Melanite, it wasn't until the battle was over that she realized that, by robotically repeating the aiming, loading, and firing process over and over, her shoulder blade and collarbone had almost shattered from the tremendous force. She pointed this out in her post-action report, which prompted the manufacturer to switch to another muzzle booster model. Only then did they have their own staff members conduct their own testing. It goes without saying that Melanite was lucky to get away with only bruises. Some of her coworkers were less fortunate. Because of flaws in their weapons' designs, some of them were injured, and some even lost their lives, and the company only gave them small, token compensation.
In the end, aside from their image, the only thing that influences a company's decisions is their bottom line. The juggernauts in the munitions industry often have higher selection standards for their employees and consequently provide them with better benefits. If they injure themselves on the job, not only is the company required to—at least from a moral standpoint—pay an amount of compensation as stipulated in the contracts, they must also consider the cost of hiring a replacement. As such, they tend to outsource the testing of any weapons of unknown reliability. By contrast, smaller weapons testing companies operate on a completely different mentality. Their contracts offer minimal benefits and high pay, attracting the most marginalized of society who just want to make a quick buck. Conveniently, Columbia has no shortage of such people.

[Classified Log]
Regardless, Melanite's railgun was likely to infect its user with Oripathy prior to Rhodes Island's modifications. This wouldn't have required testing; there is no way that the manufacturer didn't know about this.
The only conclusion I can draw from this is that they never intended to test whether the user would be infected, simply how long it would take. And if it took long enough, they could claim the weapon as safe...
They aren't crazy. They just never valued human lives to begin with.

Once, there was an old veteran who retired from Blacksteel Worldwide. After losing his arm, he took home his firearm and a hefty compensation, reunited with his wife and daughter, and started a small sundries store.
One night, the man's daughter was woken by a loud, angry yell. A group of travelling burglars had barged into the store. They were under the impression the one-armed owner would give in without a fight, only to find the man stubbornly resisting.
The ever-calm daughter went to the drawer and found her father's prized firearm. She loaded it just as her father had taught her, and aimed its barrel at the burglars, but she couldn't shoot no matter what—She just held it up and loathed how powerless she was, as her one-armed father was driven into a corner.
In the end, the neighbors, having been woken up by the fight, brought the police to the scene. The daughter was spared, though the old veteran and his wife were not so lucky...
When Melanite told the medic in charge of psychological counseling about her past, she appeared unable to maintain her usual composure. She interrupted her own story several times, hoping to compose herself, only to break down and start crying when she got to the part where she wasn't able to pull the trigger.
This tragedy completely changed the trajectory of her life. Although her relatives generously offered to pay for her living expenses and tuition, the intense insecurity she felt drove her to abandon her education. Instead, she chose to join a 'weapons testing company'—at the time, she truly thought that she might be able to dispel the nightmares that had been plaguing her with cutting-edge weaponry.
But once she started the job, she realized that her work wasn't actually all that different from a mercenary. A fair bit worse, in many ways. Even ignoring the risk of the weapons, some fight for money, others fight for hatred, and others even fight for their beliefs. As for her, she aimed her weapons at others and pulled the trigger solely to test their effectiveness—in other words, she killed for the sake of killing, as though the act of killing had value in and of itself.
Day after day, her personality grew colder and colder, alongside both the insecurity she felt in her heart and the complexity of her self-rationalization. In the end, she didn't even know what it was that she was afraid of. Only when she was absolutely certain that she could unleash overpowering firepower at any moment that she could calm down... Her nightmares never left her. On the contrary, they became far more horrifying. This lasted until she was issued the latest so-called cutting-edge weapon, ultimately giving her both Oripathy and a false sense of security.
In a sense, her infection was the first real step towards her escape from her nightmares: she believed that the company wanted to use the Oripathy insurance payout to keep a tight leash on her, and to her this was the most evil of betrayals. If it weren't for that, she could very well have kept speeding down that highway of self-destruction until she finally crashed.

Melanite was surprised when the HR operator reminded her that she had already racked up half a year in paid time off. First, she kept verifying the amount of time off she had, over and over, and then kept checking the maximum time allowed for each leave. Next, she asked if she would need to remain on standby during her vacation, and in the end even asked if her field operations schedule and assignments would remain unchanged despite her time off... Anyway, she made it sound as though there are only terrible bosses out there.
When she found out that there was nothing to worry about for any of her concerns, she cautiously applied to take a month off.
For the first couple days, Melanite was still wary that something unexpected could pull her out of her vacation. Her routine was hardly different from her usual on-shift schedule, and she also kept both her terminal and her weapon on her at all times. The only difference was that she wasn't as tense as usual. The HR operator, seemingly both amused and irritated, reminded her that her vacation time was precious. She froze for a few seconds—evidently instinctively taking it as a threat—only to realize that the operator simply wanted her to make good use of her vacation.
In the end, she slept through an entire day. It wasn't until evening the next day that she sleepily fumbled into the cafeteria. She hungrily waited for Gummy to fry her a few sausages, but looked happier than ever. She even chatted with Gummy through the entire process. That was when she learned about Istina's book club, and she immediately went to Istina's dorm room after dinner to borrow a few books.
Since that day, Melanite has started to appear all throughout Rhodes Island. She can sometimes be seen sitting in on young operators' classes, taking a walk on the bridge, watching the Reserve Op teams train at the training grounds, reading at the Convalescent Garden, discussing perfumes with others, etc... She is still the soft-spoken Phidia she has always been, but a change has clearly occurred even though nobody can pinpoint exactly what it was.
On the last day of her vacation, Melanite went to the HR operator.
'Want to extend your vacation? You look like you've been enjoying your time off.'
'I think... there's no need.'
'That's fine, too. Nothing wrong with saving up time off for your next vacation.'
The HR operator stared at her face for a while, afraid she would take something out of context again. Fortunately, she didn't.
'Right, Melanite. Everyone's said you've changed, and it feels to me something's different about you, too, but none of us could pinpoint exactly what it was.'
'Really?'
'Right... Anything come to mind?'
Melanite frowned and thought about it a little. Suddenly, she smiled.
Upon seeing her smile, the HR operator realized that it had been a month since the last time she saw Melanite's railgun.