Like Cielo, Sol considers herself to be advanced; however, she does not consider herself a narcissist, and speaks in a refined manner. This allows her to be more stable if things do not go accordingly to plan.
She maintains a love/hate relationship with her sister Ai, both praising and disliking her at the same time. She also enjoys tea.
Ai's sister, Youko was battling Chimera when she saved Ai from an accident. This severely injured her, to the point where it damaged her internal organs and made her sterile. She began to harbor anger towards Ai, and Taiki saw her true emotions and offered her the chance to be a Chimera, which she agreed to. After turning into a Chimera, she disappeared and changed her name to Sol.
She is first seen in the Move Shopping Mall, where she stalks Valkyrie Force before appearing in front of them. She reveals that she is part Chimera and warps her hand as proof, before siccing several Chimera at them. When the Chimera are defeated, she takes her leave.
Sol continues to appear before the Force multiple times. At the Fujimino Air Base, Sol and Cielo encounter Valkyrie Force, who were deployed to stop them. The two split up, forcing Asahi to divide his group to pursue them. However, Coo told him of her plan, aware that they were trying to lead them into a trap, so Asahi had his group pursue Sol only.
When Sol encounters Asahi's initially divided group, the remaining members appear, surprising her. She calls for several Chimera to aid her, but they are eventually defeated. Asahi attempts to apprehend her, but she is saved by Cielo, who did not encounter the other part of the group. They take their leave. Away from the air base, she reveals that she has collected the necessary data, though the Force's increasingly erratic actions almost endangered them.
It eventually ends at the Kudan Complex where intel reveals that she has been spotted there. Upon being confronted, she decides to go with them as she is at a disadvantage, but to honor Cielo's sacrifice, puts up a fight with two Gigas Grand Chimera. Upon being defeated, she allows herself to be apprehended. At the base, she reveals to Asahi that the military worked with Quo Vadis, and that the Valkyrie System is part of Project Messiah; determining and selecting an "Eve". She is unsure who was picked, but taunts Asahi to make the decision of sparing or killing "Eve".
After Asahi decides who is actually "Eve", Sol breaks out of her containment cell just as Miyako was preparing herself to kill "Eve". She reveals who "Eve" is, before fleeing. Asahi and the remaining members chase her, where she reveals her allegiance with Taiki, who had secretly masterminded the events of the game. She leaves with "Eve" and Taiki after he sends several Chimera at them.
At the Kasumi Biological Research Lab, Sol is confronted by Valkyrie Force again. She reveals why she loathed Ai, and that the incident she had as a human prevented her from being a candidate for "Eve", though she wanted to take care of the new Chimera as if they were her mother. Initially battling in her human form, she goes berserk and turns into her Chimera form.
After being defeated in this form, she fades away as she had went past her limit. In her final moments, her sanity returns. If Ai was not "Eve", Sol apologizes to her for being a bad sister. If Ai was "Eve", Sol asks Asahi to apologize to Ai on her behalf. Regardless, she fades away into oblivion.