Japan would do better if birth control was banned? They don't need more unwanted children. If they actually need population, they can increase immigration or incentivize and encourage people to both have and want children. Maybe not work people to death so much so they have time to spend on romance and families.
Obviously "a jungle with no people" is ridiculous hyperbole. They've tried a few minor things without reforming the cultural issues that have contributed to the decline in births. What difference does it make if the people they bring in aren't ethnicity Japanese? Are you concerned that the Japanese will die out like an endangered species? On a long enough timeline, all ethnicities are doomed, but there's no genuine concern that that will happen to the japanese any time soon.
Yes and it's the natural extension of modern lifestyle. The invariant is that for as long as there's kids, they are taken care of, and it still holds true for "jungles". How many humans do you even need?
