Not to sound too cocky or anything, but if Isaac were me, I'd just let him switch primaries like it was nothing but there were pros and cons to doing that.
Sure, a tachi had more reach and power, akin to the advantages of a katana to a wakizashi, but there was this adjustment period of sorts when changing into something new, also akin to switching gun platforms—AR to AK and vice versa—and it just might be the thing that broke the camel's back.
Additionally, Isaac's fighting style was geared towards just doing straight-up melee—only using his gun less than 1% of the time—and on paper, having something to supplement your fighting style was key but in the real world, it could spring a lot of problems.
But yeah, also in the real world, it wasn't like he was only allowed to use one weapon because Tatiana was the most versatile in our crew, switching from a semi-auto shotgun and an AK to a bastard sword and an injector axe—not to mention the knives she'd pull out from time to time and her sidearm.
I thought for a bit before I gave him an answer:
"I'll buy it for you but you can't use it outside until you've swung it enough times."
"For real?! Fuck yeah— wait. How many times should I—"
"You know the basics I thought you, right?"
"Yeah?"
"And the dailies you need to accomplish?"
"A thousand swings on all directions each day including a thousand thrusts with a soaked bokken."
I nodded approvingly, "That's right. You're doing the same thing with a longer bokken now but you're doing it on top of the thing you're already doing."
"What— That's it?"
"Yeah."
Royo mentioned from the side, "That's so fucking cool..."
Isaac asked, "For how long though?"
"What do you mean how long? You'll be doing that for the rest of your life now."
Isaac was a little taken aback but he slowly nodded his head, "That's true... I kinda get it—"
Thomas cut in, "How can you be sure he does everything you say? You keep watch over him or something?"
Isaac answered while glaring at Thomas, "I just do, okay?! It's a trust thing!"
"Riiiiight."
I chuckled, "It's true that I can't watch over all their training but it just shows when we spar. It's very little increments but hey, who suffers if they don't do the shit they were supposed to do?"
"Ah— Umm... It's umm... C-Curved a little more?"
"Ding! Ding! Ding! That's right! It's curved a little more but even though there are tachis that are less curved than katanas, they were originally designed that way because it'd be easier to draw one-handed while riding on horseback. Any idea what came first though?
The tachi or the katana? Anyone from the Marine's side? Chicago?"
"Me? I-I dunno—"
"Just guess?"
"The uh... The katana, I guess?"
"Can I ask why you guessed that?"
"Well... I heard that metal was pretty scarce back then and the quality was not as good so they probably made things shorter? Did I get it right?"
I nodded a few times, "That's a good line of reasoning but tachis were made first, unfortunately. Katanas were made in the warring period when numbers meant more-- meaning, more soldiers needed to fight on foot aside from horseback, and even though there are slight differences or inaccuracies from the history books, it was believed that uchi-katanas were made after tachis."
"Uchi-what?"
"It's the actual name for this piece of art because simply 'katana' was an umbrella term like people use for longswords. It's a small detail I wanted to add in so... the more you know."
"Oh..."
Megan raised her hand, "Wait, I thought we were talking about their differences?"
Alexa commented, "We are in a way though, right?"
"Eh. Megan's right in a way but I just wanted to add a bit of history lesson for all of you. But yeah, aside from the length and the time they were created and used, what else is there?"
As I asked the question, everyone else was looking at me for clues but I waved them off before they veered off the right path.
"Holdup don't look at me for clues because what I'm doing right now is different from how it's usually done. Ah— It's a clue in a way but—"
Kaley joined in, "Is it the way you carry them?"
I've never been so happy, "Bingo! There's a very subtle difference but I do wear mine very differently, no?"
"..." Everyone thought otherwise as they shook their heads.
"Need a comparison?" I turned to Isaac, "Hey, stand next to me."
"How will that— Oh!"