What makes history (Hijikata x OC)

Mathematics

I giggled when Sanan gave me his trademark lopsided smile. My interpretation of Kondu's temper curve caused amusement to dance in his grey eyes.

The Colonel's wicked sense of humour reminded me of home; it was subtle, cynical, and downright incisive. I had surprised myself to laugh more in our brief encounters rather than of the Baka trio's antics. I could understand why Kondō, Sanan and Hijkata represented the core of the Shinsengumi. Their friendship went beyond complementarity; there was an intelligence, there, that allowed them to relate to one another.

Not than the unit Captain didn't possess it. They were just ... younger, and louder. Expect for Saitō, perhaps, whose discretion hid a keen sense of observation. As for Sōji's inner sense of mischief ... well. I wasn't in the mood to deal with that right now, for a new challenge had been delivered upon my doorstep. Sanan's friendly banter had caused me to draw an axis of Y and X that crossed in the inner bottom of a sheet.

On the X axis, we measured the level of provocation.

On the Y axis, the damage ensued by the man provoked.

So far, I had traced a line representing Kondō-san, with a negative start. A straight line that showed how patient he was, and how his temper would rise ever so steadily, like a Sherpa climbing the Everest, one step at a time until he found himself angry without even remembering how he got to that point. My analysis had caused Sanan to chuckle. Especially the mention of his friend's obliviousness.

The bespectacled men now eyed me mischievously, the corner of his lips matching the twinkle in his eyes as he patted the paper again.

"Hijikata-kun, now."

Besides the exercise – none of us got to work on our theoretical maths often – I suspected Sanan to prod my feelings about the organisation. I played the game; there was nothing, here, that could be detrimental to the Shinsengumi, or the future. So I traced a beautiful logarithm curve; it shot out from the abyss around the base of the coordinate system, only to level out the further we went on the 'level of provocation axis'.

"Mmm, interesting."

I doubt Sanan realised how professorial he was; he reminded me of a university teacher. Curious, asking open questions, and quite the pedagogue. For a moment, I felt saddened by the inevitable fate that awaited him. The fury form would either claim his life, or his sanity. He would die by his enemy's hand, or his friend's.

"Frances-san?"

I blinked.

"Yeah, right. So, erm. This isn't a standard logarithm, you see. More like a Ln (5x), at least, because Hijikata-san bursts into flames at the slightest provocation."

Sanan hummed, neither agreeing, nor disagreeing. That analysis was a little bitchy, but Hijikata was getting on my nerves those days. Overall, it was exaggerated. For sure, he owned a serious temper, but I'd seen him make astounding efforts with Heisuke, or even external provocations.

I traced the line with my hand, showing how the curve flattened in the end. Aside from the joke, this was the most important part of my analysis.

"But as provocation grows, his actions cannot be proportional. I doubt he'd go much further than a straight kill. You can't be deader than..."

I froze, realising what I was about to say. Can't be more dead than dead ... except when choosing to prolongate your life beyond its span. Sanan's grey eyes pinned me, and my breath caught in my throat; he didn't seem angry. When had this man decided that his fate was worth than dying? How had he found the courage to become the first subject of his experiment?

The Colonel just nodded, waiting for me to go on. So I swallowed my blunder and returned to mathematics. Those were safer waters than ethics.

"I doubt Hijikata-san would resort to ... anything worse than ending another's life."