Nakashima Oil appears to be a legitimate company, but this "job offer" is almost certainly a scam. The person on the other end of this is likely using Nakashima's branding to give the whole thing an air of legitimacy, but they are not actually an employee of the company - the same way that many scammers will pretend to be representatives of Microsoft, Best Buy/Geek Squad, Norton, or other legitimate companies.
If Nakashima needs an employee to be in charge of collecting payments in a foreign country, they will most likely promote someone internally or select from applicants; they won't send people unsolicited job offers. Moreover this will almost certainly be a full-time position, not a part-time one. The scammer is fishing for people who will read this and consider it to be an easy, extremely well-paid part-time job and take the bait.
Should you respond to this and engage the scammer, I'm guessing at some point they will send you evidence of a paid invoice of, say, $10,000 (possibly by posing as a client of Nakashima that received the invoice from them) and then instruct you to send $10,000 minus your 6.5% "commission" to another bank account. Of course, whether you do this or not, you will never see a dime of the client's money.
EDIT: Actually, I can't find any news search results for Nakashima Oil. That doesn't seem right for a company which is apparently winning North Sea oil contracts. Perhaps the company itself is illegitimate as well.