I'm not sure exactly how they portrayed Luthor, but most of Akiko's activities are relatively above board, with diverse financial holdings. Her involvement in Mangatown would likely be considered a protection racket, but not in the traditional "Chicago" way. I see it much as Wikipedia describes the Yakuza influence in parts of Japan:

"Until recently, the majority of yakuza income came from protection rackets in shopping, entertainment and red-light districts within their territory. This is mainly due to the reluctance of such businesses to seek help from the police. The Japanese police are also reluctant to interfere in internal matters in recognized communities such as shopping arcades, schools/universities, night districts and so on. In this sense, yakuza are still regarded as semi-legitimate organizations. For example, immediately after the Kobe earthquake, the Yamaguchi-gumi, whose headquarters are in Kobe, mobilised itself to provide disaster relief services (including the use of a helicopter), and this was widely reported by the media as a contrast to the much slower response by the Japanese government. For this reason, many yakuza regard their income and hustle (shinogi) as a collection of a feudal tax."

So it's not simply a one-way street, and the citizens of Mangatown aren't paying for protection *from* Akiko's people. She doesn't tend to target the little guy... she definitely thinks big. If someone in Mangatown doesn't want to pay, I doubt there are direct reprisals... more likely the other merchants and residents are encouraged not to do business with said person. Akiko likely directly or indirectly owns much of the shops and properties in that section of the city, so one doesn't really want to piss off the landlady. Narratively, this side of her operation is more for the local color of Mangatown than an important part of her empire.

She's not much for violent crime when it's not necessary, and abhors the drug trade (that's Camellia's racket.) I would say she's likely involved in some large scale hijacking of international shipments from time to time, money laundering, insider trading, black marketeering, and so on, usually not just as goals in and of themselves, but as part of a larger strategy against a government, corporation or market segment.

Her main method of operation includes gathering all the information she can about everything, which suggests that extortion would play a large role in her criminal operations. Again, from Wikipedia:

"Yakuza frequently engage in a uniquely Japanese form of extortion, known as sōkaiya (総会屋). In essence, this is a specialized form of protection racket. Instead of harassing small businesses, the yakuza harasses a stockholders' meeting of a larger corporation. They simply scare the ordinary stockholder with the presence of yakuza operatives, who obtain the right to attend the meeting by a small purchase of stock. They also engage in simple blackmail, obtaining incriminating or embarrassing information about a company's practices or leaders. Once the yakuza gain a foothold in these companies, they will work for them to protect the company from having such internal scandals exposed to the public. Some companies still include payoffs as part of their annual budget."

Now, when dealing with other criminals, she can get rough. I'm sure there's more blood on her hands than some people might guess.