Duster is sent to Osohe Castle by his father Wess to recover the Hummingbird Egg, although he deliberately refrains from indicating what Duster is being sent to retrieve. When Duster returns home with the Noble Spitoon, Wess scolds him and orders him to return to the castle, this time accompanying the somewhat inexperienced thief on his task. During this venture in the castle, the then-obscure Pigmask Army are discovered to have locked down the zone in their search for the Hummingbird Egg, resulting in Duster and Wess being confronted by numerous Pigmasks, as well as one of their Claymen. It is at this time that the thieves encounter Kumatora, who Wess reveals was formerly the princess of Osohe.