Torridge visited Natsutani and Waka in prison for us. Though Waka was silent, Natsutani had this to say about his motives for his frivolous lawsuit:

Fine, I’ll tell you. I was hired by someone who called themself the “Ultimate Byakumon Trainer.” They told me to target you specifically, because they knew you’d be a threat to their plans.
And when Torridge asked who this “Ultimate Byakumon Trainer” was, Natsutani simply said:

You’ll know them when you see them.
So Gef’s hunch was right. There was indeed a mastermind behind this Byakumon business, and because of our nature as a monster extermination business, they deemed us a threat.
My next course of action was to head back to Hakuraku, Yokohama, where the Byakumon fad was at its zenith. Maybe I’d get the answers I needed if I visited that place.
What I saw on my way there was something I didn’t expect.
And just like that, I found my culprit. All I had to do was approach them discreetly.
That would be easy enough. I turned into a puddle.
Then, I squirmed my way through spectators and made it to the podium where this Ultimate Byakumon Trainer stood. Just to make my presence known to them, I surrounded them. They’d get the memo that an undine was at their feet.
Soon enough, they noticed. I’m not going to call them the Ultimate Byakumon Trainer anymore. How does UBT sound? UBT walked away from the podium while the fight continued, and I led them to a less crowded space. The back of some building would do.

What are you doing? Don’t you know I have a tournament to oversee?
I turned back to my humanoid form.

Oh, I know you. You’re that spirit we chased out of here a while back.

And I’m assuming you know why I’m here?

To stop our fun. Why else?

Look. I just want to get to the bottom of why you’re trying to get rid of the Mongoose Revolution.

Oh? You got any theories or something?

As a matter of fact, I do.

First, you waited for Alchias to make his announcement, and then you set your plan into motion. That plan? To promote the use of monsters in everyday life. To make them more approachable to the masses, you decided to call them Byakumon. You knew that The Mongoose Revolution would threaten your plan, since we exterminate monsters for a living. Because of that, you wanted to eliminate us. To that end, you enlisted the help of a few humans.

First was Natsutani Shin, a con artist and alleged loan shark. He used our CEO’s naivety against him and almost got us into severe debt, which would soon turn to bankruptcy if I didn’t intervene. He then got locked up in jail.

Second was Kurashiki Mika. While she wasn’t directly your pawn, she was one of many people who got caught up in the Byakumon craze, and she even stopped me from investigating Hakuraku any further.

Third and last was Waka Ryujiro. He tried to sue our company for damages, but it turned out his case was faulty the whole time. So he got arrested too.

But all of these attempts to stop us, faulty or not, could only have been orchestrated by someone who had a huge stake in it, and knew about these monsters before the seaside incident. That person is you,
the Ultimate Byakumon Trainer!

My, my, that was a spirited little tirade. Looks like you hit the nail on the head.

So I’m right? You’re the one behind this all along?
UBT tilted their head and crossed their arms. The mask was effective—I couldn’t tell if they were frustrated, tired, or even impressed that someone pieced their plot together.

You got it. This Byakumon business is my brainchild, and Natsutani and Waka are my subordinates.
UBT reached their hand out to me, as if waiting for a handshake.

Where are my manners? I forgot to introduce myself. The name’s Paleodictyon.

Paleodictyon? That’s a mouthful.

A trace fossil. Just the vestige of a being that was once there.

You think you’re so mysterious, huh?

I have to keep my identity a secret.

From whom, exactly? Us?
Paleodictyon made a shushing gesture. Then they seemed to look at their watch.
Attention, tournament-goers. This might come off as a surprise, but there is currently an unwanted guest affiliated with The Mongoose Revolution nearby.
I hurriedly turned back into a puddle. This couldn’t be good.
If you see a spirit with white hair and a pink trench coat, subdue her immediately.
I quickly slithered away from the scene. I assumed Paleodictyon knew they couldn’t catch me by themself, but now I had a target on my head. Once again, I was chased from Hakuraku, and I was forced to return to the The Mongoose Revolution.