Kasuga Nana came into the possession of a barrel of sake lacking a tax stamp, the seller claiming it had "fallen off a cart". Upon opening it, however, it was found to be packed with gunpowder. Investigating the matter it was found that the seller apparently had made off with several barrels but was totally unaware of the contents. He had paid off a carter to "lose" a few barrels from a load on its way from the docks. The carter in question working for a local haulage company located in the Merchant Quarter, Ryo Cart Owari.
Ryo's records indicate that the shipment the barrels went missing from was supposed to be picked up from a ship at the Northwest Dock owned by a man named Kazuki. From there it was supposed to be taken to a nearby warehouse, Ichiban Storage.
Investigating Ichiban Storage showed that they had a number of other goods that were not listed on official records. The majority were of little consequence, untaxed sake, foreign goods without tarrif paid, etc. No gunpowder was discovered. However a barrel was found stamped with a blue oni symbol. Inside was grain but buried in it were several large parcels of Blue Flame.
The foreman stated that sometimes "extra" goods arrive unexpectedly that do not have a manifest. They are not logged into inventory but are simply passed on when someone comes and specifically asks for them. Occasionally they vanish overnight. The employees intentionally do not pay too much attention when this happens.
The warehouse was in a state of flux as the owner, Shuji, a merchant vassal of Bayushi Korechika, had recently been found drowned in the river in a fishing accident. Thankfully his body was spotted and recovered by sailors on a barge belonging to Sharp.
Kazuki was found by his ship. He claimed to frequently ply the waters up and down the River of Gold along with trips to the Islands of Spice and Silk. On one of those trips he made the acquaintance of a gaijin in Toshi no Inazuma named Matéo Cardoso who hired him to carry some goods directly to Ryoko Owari. He has since taken on several shipping contracts from Cardoso finding him a reliable business partner. Sneaking onto the ship, Kasuga found nothing suspicious and that his logs support his story.