Asterisk's cycle is intended to reset Earth's climate.
Zazz's logs imply that climate change was so drastic that the heat wave melted people even if they were in cryostasis pods. Asterisk himself claims that when he invaded Earth, the planet was already uninhabitable because of humanity. Despite that, he allowed Zazz to live and attempt to preserve some of humanity. It's possible his cycle consists of humanity prospering at the expense of the environment, only for him to wipe most of them out so that the environment can heal before they can become too powerful again. However, this is possibly jossed, since if Virgo is brought to her Faceless boss door, she will state that Asterisk enacts these cycles of evolution and destruction for his own amusement rather than out of any good intentions.Yuuki Sanda's imprisonment.
In The Stinger, Yuuki is assigned as Akari's cellmate, but the dialogue never mentions why she's in prison to begin with. She does mention that she's no fan of the previous regime, so she's likely not a political prisoner. Considering how happy-go-lucky she is about her situation, it's possible she voluntarily went to prison on behalf of the state to rehabilitate Akari, protect her from other prisoners, sabotage any attempts at a jailbreak, or all of the above.At least some of new species are actually descended from humans.
It's unknown how long Asterisk's cycles are, but considering how long it took humans to evolve, it seems unlikely that so many sapient species could appear in less than six million years after most life on Earth went extinct. It's possible some humans managed to survive the extreme climate disaster and eventually evolved into the species seen in the present.Alternatively, the new species aren't actually new, but rather, the survivors of previous cycles.
Virgo claims Asterisk starts another cycle when the current civilization is advanced enough, which means it's possible humans weren't the only species to be attacked by the demons. This could add another layer to Zazz's racism, since he likely believes that because Asterisk is an Invincible Villain, humanity can only hope to prosper by tearing down the other species rather than opposing the demons. This would also explain why the ruins near bonetown have a statue of a primordial kolfos, which could be from previous cycles.