First, consider the role the OC will play. If it's a partner for Genos, think about their combat abilities. For example, if Genos is mainly a physical fighter, the OC could be a support with long - range attacks or healing powers.
How about Alucard from Hellsing? He is an extremely powerful immortal. In a crossover with Genos, Alucard's centuries - old experiences and his complex relationship with humanity could play off well against Genos' more recent creation as a cyborg. They might start off as adversaries, but then find common ground in their fight against a greater evil. Genos could learn a lot about the nature of immortality from Alucard, who has seen so much over the years.
Douluo Continent IV Ultimate Douluo was a popular fantasy novel written by the Tang family's Third Young Master and published on Qidian Chinese website. The story was about a child who hatched from an egg and unexpectedly rebuilt the divine realm with his powerful talent. This book could be read or listened to on the Qidian Reading App. The audio book recommended a rich voice and fine post-processing. The dubbing of the male and female protagonists perfectly matched the original setting. Now, you can even get an experience member by going to Qidian to listen to books! You can read authentic books and listen to authentic audio on the Qidian Reading App. The male lead was Lan Xuanyu. He had extraordinary talent and was both cute and cold towards his enemies. The female lead was Bai Xiuxiu, a cold and aloof school belle. After a hundred thousand years of cultivation, she had become an adult soul beast.
Female Genos could be developed with a more empathetic side. Since she is a cyborg, she could struggle with understanding human emotions more deeply. Maybe she starts to learn about love and friendship in a different way compared to male Genos. For example, she might be more sensitive to the feelings of other female characters around her.