Before it all starts, Kou is a bit of a brat. Ryuuko scolds him. After it’s all over, Kou is still uncertain of his place. Ryuuko reassures him.
"KOU!"
Kou dashed down the hall, laughing, and dodged around a startled Ryuuko-sama to hide behind him.
Shirogane has a plan to buy them all time and reinforce the boundary between worlds, provided Ryuuko agrees, and provided Shirogane can bring himself to carry it out.
Shirogane settled his hat back on, speaking from under the brim of it. "You and I are the direct kings. Weakened or not. If we take an action together that resonates through our realms, that may reaffirm the balance for long enough."
In the final confrontation with Homurabi, Ryuuko returns. Afterwards, Akira finds that he remembers and understands a few more things. One of them is why Shirogane has refused to make any more shin than him.
Whenever Akira had changed in the past he’d been too occupied with, most usually, almost dying to notice before he was suddenly waking up again. This time was different. This time, Akira could feel it happening, like walking down a see-saw and reaching the fulcrum, the tipping point, when uphill suddenly became downhill and the world turned over.
Akira, Ryuuko and Shirogane get some closure, and some reopening.
Akira lay in Shirogane’s arms and wondered if humans, or shin for that matter, could purr. He felt like he wanted to try. The sun had gone down, but the air was still clear and warm with spring, and Shirogane’s hands were just that comfortable bit warmer as they slid up and down his back and over his shoulders.
"The shadow in you is thinning," Shirogane murmured against his hair.