（解説文要約）
炭坑暮らしでは、朝食で、白飯に味噌汁をかけて食べることはタブーとされていました。
土木関係の作業員のほうが、炭鉱労働者よりも嫌っていたともいいます。
何も知らずに白飯に味噌汁をかけると、ベテランの同僚からこっぴどくやられたそうです。
半殺しの目にあう者もいたようです。
It was taboo to eat steamed rice soaked in Miso soup in coal miner’s society.
While this was a well-known habit of many Japanese households,
construction workers hated this style of breakfast even more than coal miners.
Not knowing this tradition, some new miners were almost beaten to death by other senior colleagues for taking breakfast in such way.
Sakubei assumes the reason why they detested it so badly was that the sight of the rice piled up in soup resembled a burial ground.