Sarakin 

Loan sharks are moneylenders who offer unsecured loans at extremely high interest rates for profit. Since most countries tightly regulate moneylending practices, loansharks often operate outside of the law. They’re notorious for using underhanded tactics to enforce debt collection from their borrowers, ranging from intimidation and blackmail, to threats and outright violence.

In Japan, private moneylending companies are regulated far more loosely than banks, needing only to follow bare minimum requirements, such as prefectural registration. Thus, they can operate with near-impunity while still being legally permitted to practice. These legal loan sharks are called sarakin (サラ金)—a portmanteau of "salaryman” (サラリーマン) and kinyu (金融), meaning "loan" —and are notorious for charging exorbitant rates and having them skyrocket within short periods of time.

The number of sarakin borrowers rose sharply around 1992, after the collapse of Japan's housing bubble led to perpetual economic stagnation, beginning an ongoing era now known as ushiniwareta juunen (失われた10年), or The Lost Decade, now commonly referred to in the plural Decades, as there's still no end in sight. This led to Japanese banks becoming more stringent about offering loans, as well as increased unemployment and economic insecurity for Japanese citizens. Japan’s most desperate—particularly small business owners, people with poor credit scores, and those struggling with addiction issues—increasingly found themselves turning to sarakin for financial help, and that trend has continued ever since.

Taking out loans with sarakin has shackled millions—roughly 14 million, or 10% of Japan’s population—to a cycle of endless debt and relentless harassment. During the start of the Lost Decades, sarakin were closely linked to yakuza crime syndicates. Employees would aggressively bully and harass borrowers, at one point even showing up at their homes, workplaces and family events with loudspeakers. The ensuing distress and despair these collection tactics cause borrowers is commonly called sarakin jigoku (サラ金地獄), or “loan shark hell.” As a result, sarakin borrowers’ mental health often deteriorates, resulting in both a high suicide rate and, in some cases, violent crime.

Although regulations and laws against predatory moneylending have increased over the last decade in response to public outcry, sarakin and their societal consequences are still a prominent social concern that remains a key issue in Japan’s national politics.

Sakaki Doburoku, coach for the Deimon Devil Bats, accrued 20 million yen (roughly 200,000 USD) in loan debt three years before the start of the series.

Judging by the unusually large amount—even compared to his own track record of frivolous spending—and how he felt the need to flee the country with no intent to return, it’s possible that Doburoku took out loans with one or more sarakin. Hiruma’s sweeping jackpot during the Devil Bats’ trip to Las Vegas paid off Doburoku’s debts, making him in debt to Hiruma instead.