After successfully synthesizing tiny diamonds in Corn City, the Kingdom of Science faces the next challenge: obtaining larger, natural diamonds to serve as battery replacements for the Petrification Devices (Medusas). Their target is the mineral-rich region of Araxá in Brazil, where they simultaneously plan to build a city for rocket production. The journey there is conducted under strict radio silence to avoid alerting Stanley. However, Dr. Xeno secretly sends an encoded message to his former follower, who then abandons the direct pursuit to intercept the team in Araxá.

Meanwhile, efforts focus on the precise processing of the natural diamonds. The realization that the harder synthetic diamonds serve as ideal abrasives enables the watchmaker Joel and Master Kaseki to grind the raw diamonds into the exact shape of the original Medusa batteries. A crucial breakthrough is achieved through the observation that all original diamond batteries have a precise cleavage point – a weakness in the atomic structure that appears to be essential for the devices' functionality.

In anticipation of Stanley's arrival, the team prepares a desperate plan: the "Fortress Medusa". This involves, in the event of an attack, allowing themselves and the enemies to be petrified together by a remotely activated petrification beam, to subsequently be revived by a hidden ally. The success of this plan now depends solely on whether it is possible to reactivate a functioning Medusa with the newly discovered cleavage point in the diamond before Stanley's elite unit arrives.