Is there ANY reason to believe that this 'Ukyo' is genunely trying to return the "lost" coins?
No proof available. Only his word.
The reason why people may retain different opinions on some issue, no matter how much they debate, is that there are some things that one learns over an entire lifetime, that cannot be easily translated into words. Because of that sem-conscious and diffuse prior knowledge, two persons can reach categorical but radically different conclusions from the same data, and neither can explain to the other why his conclusions are "obvious" to him.
How to recognize a scammer is an example of such unexplainable prior, it seems.
Obviously anyone who engages that "profession" must be very skilled at convincing targeted victims that he is honest. Therefore, one cannot tell whether someone is a scammer by paying attention to what he says. One must note
what he does (and fails to do), and to
what he doesn't say.
I can't hope to convince anyone of my "fuzzy algorithm" for recognizing scammers. But the first basic principle may be logical enough: If someone has got your money, and does not deliver the goods he promised to, you should assume that he is a scammer, until clear proof to the contrary. From that point on, you should ignore all his claims, explanations, and excuses, unless they are confirmed by clear evidence or other sources that he cannot have manipulated. Add more points every time that he refuses to give details or proof of his claims, every time he makes a promise and instead delivers another excuse, every time he avoids dialogue with curtomers or reporters. There is more, but you get the idea.
Moreover, if a businessman failed his part of a contract and owes you goods or money, you should not waste time learning
why he did not do it. His failure, by itself, entitles you to take legal action against him. That is why the courts are for. If he has to borrow money or sell his car to make good on the contract, that is his problem, not yours. "Legal action" may vary depending on the country, e.g. it may be proper to report him first to the Better Business Bureau, or seek a small-claims court.
There are several "tools" that scammers use, like the "be patient, I am working on it, but cannot tell you the details now", "I am under great distress because of personal/familiar problems", "I have lost a great deal of money with this incident myself", "we will resolve this issue whithin two weeks at most", etc. If he owes you 1000$, when you have almost lost the hope of recovering that money, he may tell you that, with much effort and personal sacrifice, he is returning 200$ to you -- betting that you will think "that nice fella rescued 200$ for me" rather than "that scumbag stole 800$ from me".
A scammer cannot be shamed into returning all the money he took from all his victims, no matter how much they complain, in public or in private. Him doing so would make as much sense as a fisherman dumping all his catch back into the sea for pity of the fish, a gold miner burying back the gold that dug out. Bad press does not bother a scammer. He has no reputation to lose: there will always be suckers who will give him money without even googling his name, or who will believe his stories of how he was framed, misunderstood, whatever. If he has any friends, they must be all amoral scoundrels like him.
If he perceives that some customers are about to sue him, or denounce him for fraud, he may refund them -- but
only them.
Unfortunately, victims of a scammer rarely get all their money back. Bankruptcy and civil lawsuits will probably find that the business doesn't have any assets left to liquidate. It may be necessary to criminally prosecute the scammer, for fraud or fraudulent management, in order to seize his personal property.
In order to pursue the legal route, clients must be able to prove their claims; but the scammer may have been careful to withold or invalidate the proofs, e. g. by not using his real name in the transactions. (In any commercial exchange, the part who delivers first has the right to know the true identity and address of the other part, and should never deliver without that information.)
Bitcoin payments are especially problematic in that regard, because the "bitcoin bank" does not know its customers' identities. A minimally competent lawyer could point to a transaction in the blockchain, and convince the court that bitcoins are valuable property and the blockchain (unlike email, screenshots, or PDF files) cannot be tampered with. However, how could he prove that the sending addres "belonged" to the client
at that time,, and the receiving address belonged to the scammer?
In the end, it often boils down to the client's word against the scammer's word. Then the client's chances will be much better if there are many unrelated plaintiffs with similar claims.
, many of us wont give up.
But on the psychological side it is interesting to see how easily people can be tricked to even side with the people that embezzled/stole their money!!! 
