Chronoa/Chronology

Human-Monster Interaction
In the Dwelling of Spirits, Rimuru attempts to save Shizu's students by having each take in a Greater Elemental to aid in stabilizing their energy. At Chloe's turn, an irregularity occurs and the atmosphere suddenly becomes tense. A powerful spiritual body, which is actually Chloe's future self, appears and subsequently possesses young Chloe. As a side effect, her energy stabilized.

Hero Awakening
Granbell tricks Yuuki into unsealing adult Chloe's body contained within the Holy Ark. After Hinata's death, her consciousness is absorbed into Chloe, triggering the latter's Time Travel skill. The two are sent back in time to 2,000 years ago. Keeping to the history they're familiar with, they become active as the masked hero who sealed Veldora. When the topic of what Chloe's public name would be as a Hero, she accepts the name "Chronoa" from Hinata to prevent her real name from being disclosed to the public and catching Leon's interest. As a result of the naming, Hinata's Usurper is stripped from her and integrated with Chloe; and moreover, the negative feelings Chloe kept isolated acquired sentience. Observing this, Hinata concludes that Chronoa is akin to a monster.

After Chloe's consciousness disappears and Hinata assumes control of her body, she struggles to hold back the raging Chronoa, who until then was held at bay by Chloe. Reaching the appointed time decided beforehand with Luminous, she hands the Anti-Magic Mask to Shizu and regretfully parts with her. In her last moments before losing consciousness inside the ark, Hinata thinks of the laid-back slime and with a light heart, decides to leave the rest to him.

Back to the present, Rimuru successfully placates the raging Chronoa, diffusing the situation. Chronoa goes through an upgrade into a Manas, allowing her to better manage Chloe's abilities and switch out with her anytime.

The Imperial Invasion
Chronoa assists Chloe while fighting Jiu, the latter having attempted to assassinate Rimuru. They try to eliminate her within stopped time, but fail due to not yet being able to control the power of Yog-Sothoth well, Chloe loses a vast amount of her energy, failing to sustain her adult form. With the help of Rimuru who lent them Veldora's energy to recuperate their energy, as well as Raphael's support to control Yog-Sothoth, they successfully trigger a time stop, swiftly dispatching Jiu, though the latter managed to escape in the end.

Game's End
Chronoa merges with Chloe's consciousness again and engages in battle with Phantom King Feldway. They exchange several blows, with none of them taking decisive damage. At this stalemate, Feldway confirms the presence of Sariel within Chloe, and activates their Ultimate Dominion to control her. Chronoa struggles against their attempted mind control, and spends an uncertain period within the six month timeskip the story takes, fighting against it. Ultimately, Sariel was successfully sublimated into Chloe, negating Feldway's interference with its control corridor. Chronoa also became one with Chloe's consciousness, permanently merging with her.