When Lark says that he considers Angela to be his mother.
Lark finally deciding to try and repair his old friendship with Setz in spite of how much the latter has changed, after having been stubborn on letting it be for so long.
Lark: "Although I don't know why you changed so much... I'll get used to it soon. You're still the Setz who was my friend."
Lark calling Sia his friend. Sia's surprised expression, followed by the reveal of his Friendless Background and present thoughts that maybe returning to school wasn't going to be as bad as he thought, cinches it.
Bathory just being so happy to have met Angela, thinking of the moment as magic.
Sia and Sai's brotherly talk before Sai accompanies Lark and co. to the Senate with Sai smiling affectionately at Sia who's worried about him, especially considering that they hadn't gotten much on-screen interaction up until that point.
After pondering over the depressing subject of if his father would've thrown him away if he hadn't awakened the fire spirit, Setz then smiles up at it and comments, "... It's warm." The heartwarming aspect comes from the fact that the fire spirit is Carne. Even after her death, she's still there for Setz.