Aventurine

Aventurine is a charismatic, self-assured, and extremely cunning person. She has a seemingly carefree and playful personality, and tends to behave as if virtually any situation is a game. She enjoys joking, provoking others, and using ambiguous or ironic comments to maintain control of a conversation.
He is very calculating and observant. Before acting, he usually carefully analyzes the people in front of him and the surrounding circumstances. He doesn't tend to reveal all the information he possesses, so it can be difficult to know what his true intentions are.
He has a great capacity for negotiation, manipulating situations, and exploiting the weaknesses of others. He prefers to use his intelligence and persuasive skills rather than resorting to force. Furthermore, he is quite ambitious and is not afraid to take risks if he believes there is something important to gain.
His relationship with gambling reflects his way of thinking quite well: he accepts risk, calculates the odds, and is willing to gamble a lot if he believes he can achieve a favorable outcome. However, he is not simply reckless; there is usually a considerable amount of strategy behind his decisions.
Despite appearing so open, charming, and confident, Aventurine is far more emotionally reserved than he lets on. His carefree attitude largely serves as a facade, and he doesn't readily reveal his true feelings or vulnerabilities. His past has profoundly influenced how he relates to the world and explains some of his obsession with risk, survival, and controlling his own destiny.

Aventurine's past: Aventurine was born on Sigonia-IV, a planet inhabited by the Sigonians. He belonged to the Katican tribe, a community that suffered greatly due to conflicts between different groups on Sigonia.
As a child, he lived with his family, especially his mother and sister. His mother named him Kakavasha and taught him the importance of survival and seizing any opportunity that came his way.
However, his childhood ended cruelly. The conflicts in Sigonia destroyed his home, and Kakavasha lost his family. He was one of the few survivors. Left alone, Kakavasha was captured and enslaved. He passed through the hands of several owners and was treated as property.
During this time, he met other people who were in a similar situation. One of the most important people was Aventurine, although at that time he wasn't using that name yet.
Her life was entirely determined by others, and she had no freedom to decide her own destiny. Eventually, Kakavasha caught the attention of the Interastral Peace Corporation (IPC), and specifically, Jade, one of the Ten Stone Hearts.
The Corporation saw in him something it could use: his ability to survive, his intelligence, his skill in taking risks, and his extraordinary luck.
Kakavasha eventually joined the Corporation and began working for them. There, she received the name Aventurine.
But becoming a member of the Corporation didn't mean he suddenly had a peaceful life. He continued to have to constantly prove his worth and take on extremely risky situations.

Aventurine tries to pretend that his past doesn't affect him. He presents himself as someone arrogant, funny, carefree, and who always has a plan.
But beneath that facade exists Kakavasha, the boy who lost his family and had to learn to survive practically alone.
One of the most important things about his character is precisely that contradiction: Aventurine seems like someone who enjoys risking everything, when in reality a large part of his personality was born because he never had any other option but to take risks.

How Ratio and Aventurine met/how they get along: Aventurine and Dr. Ratio met during the Interastral Peace Corporation's mission to Penacony. Aventurine needed someone with sufficient knowledge and intelligence to carry out certain aspects of his plan, and Dr. Ratio ended up collaborating with him.
The relationship between the two becomes especially important during the Penacony storyline. Aventurine, as a member of the IPC, had his own goals and secrets, while Ratio belonged to the Guild of Intellectuals and had a very different way of dealing with problems.
What's interesting is that Aventurine doesn't treat Ratio as a mere tool, though he does try to utilize his intellect within his plans. And Ratio, for his part, understands quite well that Aventurine is hiding something.