Project Build

Project Build (プロジェクトビルド) was a USB memory stick containing top secret research files by Takumi Katsuragi on the creation of the Rider System and it's accompanying gear.

History
The idea was first conceived by Shinobu Katsuragi, who had believed he could harness the Nebula Gas in order to develop the necessary weaponry strong enough to oppose an alien lifeform he had believed would come to Earth, Evolto.. After faking his own death in order to escape Evolto's demanding clutches, his son Takumi Katsuragi carried on his legacy by covertly performing experiments under the Touto Institute of Advanced Matter Physics' radar, but he was caught and fired by Gentoku Himuro from the institute only to be re-recruited by Gentoku to illegally continue his experiments as a member of Faust. However unbeknownst to Takumi, both Gentoku and Evolto himself were manipulating him into mass-weaponizing the Rider System for sinister warfare instead. Before Takumi's identity was wiped and reset, he had downloaded remaining files onto a USB drive and entrusted it to his mother, who would then unbeknownstly re-entrust them back to her own son and his friend after a struggle with Night Rogue and Blood Stalk for the files. Since then, the main files were stored onto Sento's computer in his lab.

The Process
Sometime after the Sky Wall Disaster, Shinobu Katsuragi himself had discovered the existence of Evolto and his plan to destroy Earth like he did with Mars and countless of other extraterrestrial planets. He hinted to his son that if Earth was ever the subject of an alien invasion, he would fight against them and asked Takumi if he wanted to help, and Takumi responded that he would. .

Sometime after Shinobu had began to devise a way to take down Evolto, the monster himself approached him and demanded him to restore the essences to the Fullbottles, which were depleted by Vernage prior to the ceremony and caused his plan to deviate. Shinobu began to study the blank Fullbottles and discovered that the essences of the Fullbottles could take on the properties of something biotic or abiotic. In his first attempt to defy Evolto, Shinobu created an experimental system of weapons that could harness the power of these bottles: the Rider System. At the forefront, Kamen Rider Build was the main product of this series of weapons, which after his supposed death, his son Takumi would later take on the reins of the Rider System's later developments, known as Project Build.

File 001 - Build
After completing the Build Driver's construction, Takumi recorded a video demonstration of his experiments on a secret computer file record, including a holographic combat simulation of Build's capabilities and showing its near-limitless form changing potential. He showed Build as RabbitTank Form to defeat 2 Guardians. He later showed the completed Wolf and Smartphone FullBottles and the completed SmaphoWolf form on a data card.

The Build Driver is in fact a "safe" version of the Evol-Driver that Evolto uses, which Shinobu decides to build as the "good" antithesis to it. Three completed Build Drivers are known to exist. Takumi and Sento share one, while it gets shuffled around in possession between Ryuga and Gentoku before Sento gets it back. Later, Sento builds Ryuga his own, before it's taken by Kengo Ino and Ryuga gets it back. Later Shinobu Katsuragi is revealed to also have his own, before it's given to Kazumi.

Sento later creates several adaptors that would allow Ryuga Banjou and Kazumi Sawatari to use one Fullbottle instead of two for a transformation.

File 002 - Blood Stalk
Takumi later developed a device that allowed those who could not use the Build Driver to transform; the Transteam Gun, which allowed its wielder to gain power similar to that of a Driver user. He created Blood Stalk using the Cobra full bottle as the first prototype. He noted that the system was designed to push Build's growth potential further by challenging its limitations. The system also includes a voice modulator, a feature of privacy protection for its user.

Two completed Transteam Guns exist. Soichi Isurugi uses the original advertised one to transform into Blood Stalk, while Gentoku Himuro uses the other one to transform into Night Rogue.

A much more advanced version of this weapon created entirely by Kaisei Mogami is the Nebulasteam Gun.

File 00X - Sclash System
Upon accessing the file, Takumi congratulated the viewer as he shows his latest and greatest project, the Sclashjellies, jelly-pack like containers that contain Fullbottle essence, solidified as gel. However, Takumi admitted that this technology was unfinished, and was only able to create Sclashjellies for two essences. After Sento took the reins and completed it, the research was copied and 'stolen' by Soichi Isurugi. Soichi takes the copied research and presents it to Nariaki Utsumi, who then builds a Sclash Driver from the schematics for Kazumi Sawatari, who transforms into Kamen Rider Grease. Sento then proceeds to build one of his own for Ryuga Banjo who transforms into Kamen Rider Cross-Z Charge. Later on in the war, Utsumi builds one for Gentoku Himuro, who transforms into Kamen Rider Rogue.

Three Sclash Drivers exist. Utsumi built two of them for Kazumi and Gentoku, while Sento built one for Ryuga. After the world merger, no more Drivers exist until Sento manages to rebuild some for Ryuga and Kazumi.

File XXX - Hazard Trigger
Originally locked behind a password, File XXX detailed the creation of the Hazard Trigger, which Takumi explains that it's meant to boost the Rider System power output dramatically, however prolonged usage will cause the user to lose his or her rationality due to the overwhelming stimuli in the brain, eventually inducing an impulse to destroy everything in sight. Evolto was in possession of the only one produced, before giving it to Sento. However Ryuga steals it from Sento for Kengo Ino before defeating him and getting it back.

In actuality, Shinobu had created the Hazard Trigger in hopes of developing a counter to Evolto's Evol-Trigger in the case Evolto himself had reached his monster form.

File 1 - Enigma Development Research
By inserting the keywords Kaisei Mogami, Enigma and Kaiser System, this will reveal a journal written by Takumi during his time working with Mogami. The file states that Takumi helped in the creation of Enigma and he personally did some travels to the World of Ex-Aid.

File 2 - Muteki
Project Build contains a research file about Kamen Rider Ex-Aid including the Gamer Driver, The Maximum Mighty X Gashat and the Hyper Muteki Gashat.