Rukia Kuchiki is a crucial character in Bleach since she is the one who introduces the protagonist, Ichigo Kurosaki, to the world of Soul Reapers. Moreover, she also gave him her powers and spent a lot of time training him. Her sister was married in the noble Kuchiki family, and on her deathbed, she made Byakuya Kuchiki promise that he would find and adopt Rukia. Byakuya kept his word, and his relationship with Rukia had a significant impact on the plot. Rukia and Byakuya had known each other for a long time, but their relationship was distant and cold until Ichigo turned things around. His arrival was pivotal in Byakuya’s change of heart, and he started giving Rukia the importance and value that she deserved as his foster sister.

Kaien and Byakuya

Rukia was adopted by Byakuya only because her sister had requested him on her deathbed. He just wanted to keep his word and was not emotionally invested in the decision. It meant that even though Byakuya adopts Rukia, he never was an emotional pillar worth relying on for her. Byakuya cared more about traditions and etiquette, so they hardly got to know each other that well.

Although it’s true that Rukia’s adoption took her off the streets, which was a great thing but an absence of an emotional bond with her foster brother must have made her sad; however, she was lucky to have Kaien Shiba, who taught her a lot of things. She learned that there is an immortal link between people that can outlive them. Kaien soon became the brother figure that Rukia desperately needed. It’s true that there was no moment where she was shown to be regretting the decision to join the Kuchiki family, but she must have felt left out for sure. Everything changed once Ichigo entered the picture and made Byakuya question his beliefs.

Byakuya’s Teachings

Rukia was about to get executed for the crime of sharing her powers with Ichigo. It was necessary even for the show since it led to Byakuya’s reassessment of values. He finally concluded that even though duty and tradition were essential, they could never trump personal loyalty and love. When Ichigo went to Hueco Mundo to rescue Orihime, by that time, Byakuya and Rukia were very close. He was proud of her foster sister, and she proved her loyalty by assisting Ichigo in Hueco Mundo.

Rukia, after her rescue, finally realized that she should apologize to Kukaku Shiba for killing Kaien. Although she was possessed by a Hollow when she did it, it deeply affected her emotionally. Both Rukia and Byakuya learned that the true source of purpose and strength was opening one’s heart to other people. Rukia made peace with her past and worked on her relationships. She was able to forgive herself for killing Kaien. 

Everything happened at the right time as she was soon confronted by the biggest challenge of her life. But by then, she had already become a warrior who had learned the importance of relationships and forgiveness. Rukia and Byakuya became genuinely dedicated to each other’s support when she was able to unlock Bankai. Byakuya helped her control, and his praise made Rukia cry. She finally knew that she has a big brother who will stand by her no matter what happens. 

Source: https://directoryrelt.com/blog/bleach-how-did-byakuya-and-rukia-make-peace-with-their-past/