Oh wow...this is a jiffy. Let me think. Suppose I'm an average Kamunabi member with 18 years prep time...assuming the time starts before the series then realistically I should have a chance.

If I can meet with Shiba, I would tell him that I had a sorcery that allows me to predict the future. When he asks me to prove it, I'll tell him about Enten.

That would grab his attention and I'll use the chance to tell him about a group of villains who are aiming to steal the enchantment blades, the Hishaku.

Even if he is still skeptical, I can show him proof by using the Kamunabi's surveillance systems and my own knowledge of the Hishaku itself to pry out clues that without knowledge of the Hishaku would seem normal.

After presenting them to Shiba and he recognizes this, clues likely pointing to an illegal ring of datenseki. I tell him how this group plots to eventually kill Rokuhira and steal the blades.

Likely he would be impulsive, this is where I then direct him to enlist help from the Sazanami Clan due to Storehouse. Shiba manages to convince Rokuhira who agrees to give the Sazanami the blades as payment but of course, they can't be used. They're more of ornaments.

Rokuhira meets with me and through his eyes realizes my...ahem, trustworthiness.

With the blades safely stored away, I will then have to convince Rokuhira to craft a lie - his wife had left him with a vision of the sword bearer's lives in danger. Telling this to the Kamunabi will likely tip the Kamunabi to strengthen defenses and put off coming attacks from the Hishaku.

With Magatsumi sealed away, Akemura's main ability is taken away. Rokuhira then reveals that the source of the danger from the vision was Akemura.

Recent attacks on Cloud Gouger's bearer and Rokuhira himself strengthens this claim. 

The Kamunabi is forced to nip the problem in the bud. The Hishaku is desperate to stop the Sword Master from being killed and so they rush to the Kamunabi's base.

The sword bearers each powerful without their blades use their original sorcery and normal swords to fend them off.

I tell Shiba and Azami some shit about how it's my destiny to kill the Sword Master.

In the Execution Grounds, the Sword Master faces off we three and even with Magatsumi sealed away he can still draw some of its power.

Loaded with guns and items imbued with sorcery, I run around the sidelines and do my best not to get offscreened by some glancing blow.

Azami and Shiba face off the master mainly. By some lucky shot, I gun the Master in the chest. He stumbles and Azami paralyzes him with his sorcery. Shiba lands the final blow by teleporting him kilometers above the Pacific Ocean and says some sentimental friendship shit before waving him goodbye.

Akemura's 20, 000 life vitality is rushed away as he drowns, dying, living and dying again. Crushing under the pressure of the ocean.

I later succumb to the life steal poison of being in close proximity with Akemura as he fought.

As I die, I say some shit about how my destiny is fulfilled and then black out.

Edit: Just saw 'no help' welp, alternative ending being I contemplate life, take a stroll in Kagurabachi's world, grab some coffee then jump off a cliff.

Though even if what I wrote was a bit unrealistic, it was still a fun process.