And that was how Brunilda started acting like from that point on: as a burglar that sneaked into the Crown townhome and frequently murdered the local wildlife.
Mattheus mostly left that part of their plans to her, only dropping the excuses to his family and acting grateful before staff when the cat "gifted" him presents in the form of dead dormice and birds.
(He did sit Brunilda down when she went overboard and the gardener found her dragging the corpse of a dead fox. His friend was unrepentant and only returned that it had been self-defense. Thankfully, people apparently used to eat foxes too, so none of the dead reynard went to waste. The fur was processed and used to line a makeshift bed in the lab for Brunilda, who took to sleeping on the skin of her "enemies" while cracking a joke.)
Instead, Mattheus spent most of his time trying to get qualifications to practice medicine unsupervised. He had decided he was going to at least try to help the General—in for a pound and all—which required a license to practice if he didn't want to make more trouble for the Crowns.
There were two ways to get qualifications and the only "quick" method was to take advantage of Mattheus Crown's Professorial status to speed through the process. Unfortunately, with his amnesia, he would have to prove he still had the knowledge required. They weren't going to take away the Professor title from him but he would need to have board members accept him to practice as one (in the sense of a teaching position).
So he spent most of his time reading or in the lab, half-ignoring the household being bemused over the cat that kept reappearing. He was aware that the Duchess had taken to sending a servant to retrieve Brunilda, only for it to repeat again and again. The baby sister of the King was being very considerate over Mattheus's self-imposed exile from socializing because he wanted to avoid the fallout from the royal ball.
Or maybe she was sharp enough to realize what he intended without asking? Mattheus always second-guessed the Duchess's motives due to the woman's strong resemblance to the extremely clever and competent Brunilda.
The problem was that none of this magic made sense!
At some point, he turned to Brunilda—who just came back after being retrieved (poor servant would have to make another round-trip)—who had seemed to be staring down at the open pages of a text. "Brue!"
The cat lazily lifted her head, green eyes meeting a slightly frantic pale stare. "'Sup?"
"Maybe you can make sense of this and explain it to me." Then he all but shoved the paper he wrote the notes on before her whiskered face.
There was a pause before an exasperated sigh was heard and green eyes stared at him. "I can't read that."
Mattheus automatically flipped his notes around. "I don't think my handwriting is that messy—"
"So you haven't noticed."
"Noticed what?" The man blinked.
"Maybe it's the Transmigrator occupation… Anyway, you no doubt figured this is not the past but an alternate world or reality, right? Have you not noticed the architecture and fashion is mostly Victorian England in style?"
"Well, yes, obviously." He was waiting for the other shoe to drop.
"You know England speaks English."
"Of course I—" Mattheus paused in realization. "Am I not speaking in English right now?"
There was a pause and Mattheus could almost imagine Brunilda doing a mental face-palm.
"No. You're an aristocrat. Yet Theo was born and raised in New York City. You've been speaking in an American accent and no one thought it odd. In fact, the only one with a posh accent is your new mum. Your brother, Edgar, has a transatlantic accent. You've been on the soft-spoken side acting as Mattheus Crown before others, so the original one must have had a similar accent. Alfred Crown and you talk similarly when you're not being Gen Z."
Mattheus's eyes widened in surprise. A part of him did notice the discrepancy but he hadn't thought much of it as long as it worked in his favor.
"But, wait." Mattheus started. "Wouldn't it still be English I'm reading and writing if the others are speaking English?"
"You have to focus a bit but it's not Modern English as we know it. The writing you showed me uses the Latin alphabet but the spelling is… I can parse it and I've been trying to learn to read since I arrived here, but it'd be easier if you just read it out loud to me if you're short on time."
He prepared to do so but had to ask one more question, "Is it Middle English or something?"
"It's more similar to Early Modern English but you know I have never been a fan of Shakespeare." There was that similar note of distaste from Brunilda whenever that playwright was mentioned.
"And English is like your fourth or fifth language," Mattheus finished. He nodded to himself before he started summarizing the magic system to his feline-shaped friend. "Magic is scientifically—er, academically referred to as "inexplicable" or "mystifying" energy. The educated seems to call it Occult Energy.
"There seem to be five base elements identified through color. Yellow is air. Blue is water. Red is fire. Then there are White and Black which are, respectively, life and death."
"Okay…" Brunilda followed along.
"There seem to be secondary elements that are combined from the ones I just mentioned. Green is earth and a combination of air and water. Orange is lightning or plasma, formed from combining air and fire. Purple is steam which is water and fire.
"The academic terms for the elements are Aeros, Aquae, Ignis, Obitus, Lucis, Terrae, and Fulminis."
"Air, water, fire, death, life, earth, and lightning, I assume?"
"Yes. It's Latin right?"
"Mhm. Though death and life seem to have seen some adaptation."
Mattheus made a note to ask later. It was useful that Brunilda was both a polyglot and knew more of the sciences than he did. The benefit of non-American secondary schooling, no doubt, along with her just being older and a bit of a nerd.
"The energy levels are measured in quarks and a scale—"
"What?" Brunilda cut him off.
"Huh? What 'what'?" Mattheus blinked. His brain was a little tangled from puzzling out the magic system, so forgive him for being a bit slow at the moment.
"'Quark'?"
"Yesss…?"
"That is not what a quark is."
Mattheus prompted Brunilda a few more times before he gave up getting help from that front. Until Brunilda got over her preoccupation with this world's naming sense (and how quark was an actual term used in particle physics. Really?), he would need to continue to bang his head against this world's magic system by himself.
It was going to take a while.
…
A few days later, when he was still in the middle of trying to understand the convoluted magic—which was already difficult when actual scientists in this world barely understood said energy in the first place. Because, seriously? Calling it inexplicable energy was beyond being on the nose.
Anyway, a few days later, someone visited the property.
The Duchess herself paid a personal visit. Ostensible to his mother but he was asked to drop by.
Mattheus was unsurprised how Brunilda kept running away was brought up. He made the usual excuses of not understanding but praising the cat before the Duchess told mother and son the story of how she found Brunilda.
"It was horrible to see such a lovely cat hurt and from my carriage too. So I brought her back and healed her." After the countess said a commiserating remark, the Duchess continued. "I don't know how such a cat found herself in such a situation, honestly. She looked well-cared for once she was cleaned up.
"You have memory issues due to that hunting accident a few weeks ago, no? Sir Crown." Sophily suddenly asked a non-sequitur.
"Ah." Mattheus was taken aback. "Yes."
Countess Crown was exemplary support, speaking when her son faltered in surprise. Smoothly, she replied. "Yes, your Grace. He has spent most of his time studying the past few days. I barely see him at mealtimes as it is!"
The Duchess was serene as she said, "Is it possible that Tsavorite was previously your cat, Sir Crown?"
He couldn't believe Brunilda's ad hoc plan worked. And so quickly! He had thought it'd take at least a few weeks, if not months.
"Ah, no one mentioned it to me before… but she does seem very familiar."
"You don't call her Tsavorite, Mattheus," Honoria Crown pointed out.
"Oh?" the Duchess voiced mildly.
"I was curious, your Grace. He calls her 'Brue' which honestly is very much his sense for naming," his mother said fondly. "But the interesting thing is that the cat answers to the name! She comes to the servants who call her Brue."
After a moment, the Duchess sighed before giving a small smile. "They do say cats are the ones that choose their humans rather than the other way around."
Mattheus kept his expression pleasant but internally frowned as he tried to parse the royal's comment. Did she just say she was giving over "ownership" rights to Mattheus?
The conversation continued and he had no more time to think as the Duchess asked about his studies.
"I want to become a physician, considering my abilities, your Grace. But because of the accident that gave me this ability to heal, I would have to prove that I still have the qualifications to be a Professor in practice before I can get approval to be a doctor to help the sick," Mattheus explained.
The Duchess set her tea down and sounded thoughtful as she nonchalantly dropped a bomb with her words. "I don't see why you could not practice medicine if Baron Endlewood gives his approval. It would be a travesty to keep your abilities retrained by procedure under such extraordinary circumstances."