I think some research might be in order.
In some ways the Welsh would be a closer match to the Ainu (the original minority people here in Japan), but I would opine the Welsh have fared better under British rule then the Ainu have under Japanese rule.
As to cultural differences, there would be many, as generally any Asian country will differ from a Western one. Greetings, use of directness, religion, forms of government decision making, etc. are all different.