The Final Defense Line: Minuma. Preta Can't Swim

[Core Room]

"So they're giving Musashi's Hiratsuka a wide berth after all, it seems."

Five days after the Awa army was first sighted, the enemy passed by without calling in at Hiratsuka, the Toshima Magistracy. They skirted east of it and set foot into the desert.

"Marie, when one advances this way from Kōnodai, one has to ford a dry river both before and after Hiratsuka, so they were likely wary of a water attack or some such. Whether they know Minuma exists, I cannot say."

Rāja inferred the Awa army's intent.

"That said, a considerable number joined up from Hiratsuka, so their head count has swollen quite a bit. It's hard to make out, but it looks to be over a hundred thousand. Musashi can't rein in its merchants and adventurers, granted, but a gathering of mercenaries on this scale is abnormal."

The 400 mm astronomical telescope had been repurposed for ground reconnaissance, but at 200 km the distance was still too great, and not even Mint could make out any detail. With Tsukuba Naiyaku-no-jō, the range had been 40 km.

"This is shaping up to be a far larger host than we predicted. The numbers picked up along the way almost certainly exceed Awa's own mustering capacity, so they must be mercenaries hired with coin. But do these mercenaries truly believe they can win?"

"Or they may be mercenaries from afar who don't know this dungeon's reputation for 'taking no prisoners.'"

Mint said.

"Marie-san, is it about time the drones had their turn?"

"Master, this time we'll deliberately forgo the drones and hold to a policy of not venturing one step beyond Tsuji Village. The opening engagement will be at Tsuji Village. A dungeon cannot reach beyond its sphere of influence. Since everyone takes that for granted, we'll let them misjudge our sphere of influence as ending at Tsuji Village."

Marie deliberately mothballed the drones.

"From Hiratsuka to Tsuji Village is forty ri of desert. Six to eight days, most likely. They may send a small mounted detachment or the like to probe us in force, but since our 'no prisoners' policy is known, they'll probably turn back just short of Tsuji Village. Once they enter the dungeon's sphere of influence we can pick up images and sound, so we'll have the details by the day before they reach Tsuji Village."

"If the sphere of influence reached as far as just short of Hiratsuka, I could have kept a foul, miserable rain falling on them day after day until they sickened…"

"Mint, in a desert that would be an outrageously extravagant bit of harassment. Unfortunately, Minuma doesn't hold that much water."

"Marie-san, the final defense line is just short of Kishi Village, at Minuma. That was the plan, yes?"

"Yes. We'll lay traps for each case: if they cross the bridge, if they swim across Minuma, if they detour to the weir three to four kilometers to the west, if they go through the dry valley still further west, or, conversely, if they swing around to the east. And since this dungeon's natural enemy is the Preta, we'll draw up a multi-stage plan to make certain they're finished off even if the host is heavy with Preta. We're short of water this time, but going forward, it's worth considering damming the western dry valley 'Kamogawa' as well, so the dungeon is ringed on three sides by marsh."

"Can't we surround it completely?"

"The northwest side sits at a higher elevation, but we could always dig an artificial canal there. Preta have a high specific gravity and so can't swim, so shoving them into the marsh ought to be effective. Drowning doesn't kill them, but once they've fallen into suspended animation we need only break them apart. Or we could simply bury them in the strata as they are. It isn't quite Kimigayo, but in time they'll turn into sedimentary rock."

"What of Tsuji Village?"

"Tsuji Village we'll evacuate for now. Let's make them think we've fled. But dungeon structures aren't easily broken, so there's no fear of it being seized."

After that came the finer deliberations and preparations.