An engineer who, despite his unrequited love for Cheng Xin, plays a pivotal role in humanity's future through his strategic actions and essential communication with the Trisolarans.

An AI android controlled by the Trisolarans, who interacts with humanity in various roles, providing both aid and posing threats depending on directives from her controllers.

A government agent whose pragmatic and often ruthless approach to humanity's survival puts him at odds with Cheng Xin's empathetic outlook, representing a contrasting perspective on existential challenges.

An astrophysicist who befriends Cheng Xin, offering support and a more pragmatic view on survival as they navigate the changing universe together.

Initially a scientist with minimal renown, he rises to hold a critical position of power where his understanding of cosmic threats plays a central role in the narrative.

A character who first appears among those exploring the universe beyond the Solar System, later becoming a key companion to Cheng Xin in their shared experiences and endeavors.