[If the situation weren't as dire as it was, he might have chided Bunny for that response--more for his reasoning than the callousness; Kotetsu knows it affects him more because Fai told him the whole story, much of which his partner doesn't know. But lives should always be paramount to a Hero, regardless of personal grudges. And maybe they're not technically Heroes, here, but it's too wrapped up in Kotetsu's sense of identity for him to let it go.
[ voice ]
Instead, he simply says--]
Thanks. And I will.
[...probably.]