Fukushuuya

Saki dashed through the intersecting path, two men in hot pursuit.
No, in fact, three people were chasing her.
A young boy trailed behind at a leisurely pace.
"This is weird! This is totally weird...!!"
No matter how she ran and ran and ran, they pursued.
She veered into a park. No exit. She screamed at the strangers:
"Who are you!?!"
"Me? I am---"

Fukushuya. The "revenge-takers". Nobody. A proxy. An agent on behalf of someone who paid for vengeance on their behalf.

The following day, the victim would be a girl named Aki...

[From DLsite English]