Despite the torturous burden of the Crushing, Sunny couldn't help but feel jubilant. Not only did he receive eight shadow fragments and a powerful Memory, he had also defeated a Fallen Devil all by himself, without even Saint providing him any help.
The Black Knight, too, had been a Fallen Devil. So killing one solo meant a lot to Sunny. It was a poignant milestone that made him feel like all his hard work and all the vile things he had gone through were not for nothing. He was accomplishing his goal.
Growing stronger.
…Of course, the Mordant Mimic was not as terrifying of a foe in battle as the guardian of the ruined cathedral had been. One was a creature that seemed to have been created solely for combat, while the other mostly relied on deceit and ambushing its prey to achieve victory. And yet, the chest fiend was by no means an easy foe. If anything, its devilish nature only made it that much more dangerous.
'Argh!'