The Demon Eel

The main character is a married man who was in deep debt because of gambling. He had no way of turning over the situation until the boss of a shady loan company gave him a job as a debt collector because of his unusually huge body. Debt collecting was not the only work. Every now and then, he was tasked with other shady odd jobs, such as working as a driver for the prostitutes and transporting shady boxes.

One particular work location, the eel farm, gave him the hardest time - not because the work was hard, but because he was scared. The empty and run down street, the groomy employees, the man with deep burn scars and the creepy little girl gave him the warning that this street was unusual.
What was in the 60 kg box he transported (corpse?)?
What was the little girl doing at mid night in a street like this?
Why was the meat in the hot pot store so cheap?
Or were all these his imagination?
What about the charming young prostitutes who approached him? What about his wife?