Sky Master rules Synapse, the floating realm above Earth, as its primary antagonist. His face remains perpetually obscured, typically depicted seated upon a throne flanked by Angeloids. He treats these beings with extreme cruelty, viewing them solely as disposable tools for his amusement and subjecting them to relentless physical and emotional torture. His sadism includes discarding Angeloids he deems useless, dismissing them as "trash."

He harbors profound contempt for humans, whom he derogatorily labels "Downers," a perspective initially shared by Nymph. His overwhelming arrogance leads him to consistently underestimate both humans and Angeloids, frequently expressing shock when Angeloids defy his commands or break free.

His past actions include creating the "ultimate air defense system," Zeus, unveiled in manga chapter 47, as part of his efforts to dominate Earth and Synapse. He also orchestrated the death of the original Sohara Mitsuki from a childhood illness. Following this, Daedalus, using the alias "Sakurai," created a clone to preserve Tomoki Sakurai's memories of her; this clone became the Sohara who grew up alongside Tomoki.

His reign ends when Tomoki Sakurai, empowered by acquiring Ikaros's core, punches him during the final battle, an act that symbolizes Sky Master's defeat.