Anakin and Ahsoka’s relationship is a glimpse into what his own relationship with Obi-Wan should have been. Though the two start off as bickering siblings, Anakin starts to deeply care about Ahsoka and becomes a father figure to her, their dynamic changing as Ahsoka grows more powerful, even earning a higher rank — whereas Kenobi himself said exactly what he thought about the relationship with his padawan, when he called him his brother and expressed his love as Anakin was burning alive.
A big part of “The Clone Wars” is illustrating the sins and the mistakes of the Jedi that led to their fall, and there is no better example of this than Ahsoka, who literally grows up on the battlefield, experiencing the horrors of war firsthand. But compared to Jedi like Barriss Offee, who was trained to consider herself expendable and a tool of the Jedi Order, Anakin genuinely cared for Ahsoka, shielded her from the more horrific aspects of the Clone War, and raised her as more than a tool.
It helps that both have a knack for not following orders, each complimenting the other’s burst of disobedience, and bringing the best in the other. And yet, they both understood each other’s temptations with the dark side, going rogue, and disregarding the council. Ahsoka knew about Anakin and Padmé and guarded the secret, while Anakin understood her desire to walk away from it all towards the end.