The Batman had stayed for a bit to pay his respects to Frisk (and maybe, a bit, to the unknown child) but after talking with Grune he'd decided... he'd prefer to have some time alone.

Putting away the shovel and other tools made as good an excuse as any, so when he passed by the small white monster the Batman would be busy carrying those away. He was preoccupied enough with his thoughts that he almost ignored Asriel, but when he noticed how lost Asriel looked, Batman paused to give him a gruff nod.

"Asriel."