As you know most white populations in most countries are under replacement levels. Similarly Japan also has an aging and declining population. Britain is in a similar boat.
The answer is to take a page from nature. I was thinking about birds. Right now it is about 5am and they are out chirping away. It's interesting to consider what those bird vocalizations really are. They are basically yelling at the top of their lungs, "I want SEX!!" They basically yell this every morning for hours.
I think humans could adopt this strategy. If every white person opened up their apartment door at around the same time and yelled I want sex for several hours at the top of their lungs; And also made sure to walk by the park or any other place that others could be to also yell it at each other, I think the reproduction problem would sort itself out.
Instead humans wake up as late as possible to shuffle off to a job where value is extracted from them, then they go home tired.
Wake up at 5am bro. That's the key.