Synthibae (Synthi) are android companions designed to aid Mahoubae in both administrative and fieldwork. They work as personal computers with intelligent AI, capable of managing digital tasks, tracking assignments, and even assisting reapers in the field. While mainly programmed as assistants, some Synthibae develop emotional responses over time, blurring the line between synthetic and sentient.

Synthibae have ball-jointed doll-like features, combining synthetic fur and skin. They possess four 'ears'—two are fluffy and animal-like, while the other two are made of plastic and contain their data ports. Their feet are small and delicate. Embedded in their chest is a soul gem, which houses their main processing chip; any damage to this gem can cause malfunctions or system errors. Synthi have 'blood' used to keep their joints lubricated and in working order, with varying colors. Each Synthibae is also marked with a barcode number somewhere on their body for identification.

• Humanoid & Compact Forms: Synthibae typically have humanoid appearances, though they can also take on smaller, compact forms known as ‘Mobile’ forms. These forms can take the appearance of a smaller chibified version. These versions must be bought and only one form can be ‘active’ at a time. These forms are very small and can differ in appearance somewhat from the Synthibae's humanoid form. Due to their size, they have one port on their back, though most functions are handled wirelessly.
• Customizable Aesthetics: Many Synthibae are personalized with different skins, accessories, or mods to better match the needs of the person they are assigned to.
• Soul-Link Tech: Implanted in all Synthi is a ‘Soul gem’ that mimics that of normal baes and contains their main chip. It can be connected directly to a companion's spirit gem, allowing instant access to information, status reports, and mission details.
• AI Personality: Some have preset personalities, while others develop their own over time to better suit the needs of the person they work with.
• Ports: Their second set of ‘ears’ open to provide access to ports and wires used to connect to other Synthi and computers. This also serves as a charging method. Some may have additional access points along the spine for expanded connectivity or modifications.

• Glitches & Rogue AI: Synthibae can malfunction, developing unintended personalities or refusing orders. Rare cases involve rogue Synthi attempting to free themselves from SC Corp systems.
• Over-Attachment: Synthibae may struggle with their synthetic nature, forming strong bonds or resisting memory wipes.
• Illegal Modifications: Some people modify their Synthibae beyond standard programming, resulting in unpredictable behavior or unstable AI. These are strictly illegal and may result in confiscation or decommissioning.
• Emotional Growth: Some models, especially those exposed to long-term companionship, may develop quirks, attachments, or personal goals. This can worsen if the person they are with encourages the behavior.
• Corruption / Viral Infection: Some Synthibae become infected with corruptive code linked to Kumogami interference. This can happen through hacking, direct tampering, stolen units, or prolonged exposure to contaminated systems. Infected Synthi may show unstable behavior, damaged memory, or even visual signs of corruption such as warped features,  glitching eyes, or other mutation-like changes.
• Synthibae are non-living constructs, though many people treat them as companions or even friends. Some consider them potential romantic partners, though this is discouraged.