He wants more good people like Tsumiki to receive fairness and that's why he decides to save people unfairly. This helped him realize that he didn't save Yuji and you because it was logical, he did it because he didn't want to see a good person die. He knows it was a selfish and emotional decision but Megumi is okay with that because he's not a hero, he's a jujutsu sorcerer. This is why he's never regretted saving Yuji and you, not even for a second.

"I'm not a hero, I'm a jujutsu sorcerer."