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 which she never gave a thought to before, she accepts the name "Chronoa" from Hinata to prevent her real name from spreading to the public and risk attracting Leon's interest, causing undesired revisions to history. As a result of the naming, Hinata's Usurper is stripped from her and integrated with Chloe – in addition, 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 and neutralizes the threat. Chronoa goes through an upgrade into a Manas, allowing her to better manage Chloe's abilities and switch out with her anytime.