Kamito and Restias relationship. The two of them want nothing more than to be together peacefully, but between the corruption and Kamitos destiny as the Demon King, destiny keeps screwing them over. When they finally reunite, there are Tears of Joy on both sides of the Fourth Wall.
Est's devotion to Kamito nearly equals Restias. She's tries to destroy herself before endangering Kamito, and after being convinced to stay with him, is willing to become the enemy of the entire world rather than abandon him.
Claire finally reaching Rubia and bringing her out of despair.
Rinslet and Claire tend to fight like cats and dogs (pun intended). However, Rinslet repeatedly demonstrates strong affection for Claire, comforting her about fights with Kamito and her troubles with Rubia, as well as genuine Mama Bear behavior whenever someone hurts Claire in front of her.
The definitive moment comes in a side story showing their academy life before Kamito appears. When some upperclassmen torment Claire over her relation to Rubia, Rinslet summons her bow and bluntly tells them to back the hell off or get an arrow between the eyes.
Kamito reconciling with Velsaria, who he had unintentionally driven over the edge three years ago.
Though much of their interaction is snark and bite, when Greyworth collapses Kamito nearly has a panic attack and won't leave her side before he knows she is okay again.
Kamito is afraid that if people learned his identity as Ren Ashbell, many would have their image of "her" shattered. Fortunately, after Claire finds out, she tells him that she still feels grateful towards him for inspiring her to win the Blade Dance.