I really like how they made use of the eyes and contrast

Kamiki, losses his “darkness” to only be engulfed by it as he could not let go of his fleeting moment of brief happiness Ai brought, which ultimately became the “weight” that dragged him with the karma of his actions coming full circle.

Also how his life revolved around keeping things in place to chase a memory. It was a selfish gesture to make himself happy

Meanwhile, Aqua has two “white”, albeit fading, lights showing how he has finally found full clarity in his actions and can actually find true peace in what he achieved, his “weight” has been lifted as he can finally feel like that pit that has made his life horrible is finally gone as he frames his life away from darkness in revenge, to finding light in living for someone else.

They are both selfish, but the difference is one took life to chase happiness and the other gave their life for someone else’s happiness.

(Still feel Aqua has a good chance at living as he was floating to the surface, but who knows how it ends)