The whole article never mentions what the Japanese method actually is. Only mentioning that its not geometric and that you plant a bunch of plants in the same spot.
Miyawaki method. Basically chaos gardening. you either cast a mix of various native seeds or closely plant saplings of native species, and let them compete naturally. Resulting in a dense lush biodiverse forest.
The “Method and conditions for success” section of Akita Miyswaki wiki has a basic outline of the method https://en.wikipedia.org/wiki/Akira_Miyawaki
From the comments link:
From the article: the Miyawaki method, a forestation technique that creates fast-growing, highly biodiverse native forests in the middle of urban areas, or even on deteriorating land. This planting style forces vegetation to compete for resources, accelerating its growth. A forest planted using this technique can grow in 30 years and requires no maintenance after three years.
Wikipedia: https://en.wikipedia.org/wiki/Akira/_Miyawaki#Method_and_cond…
A dense plantation of very young seedlings (but with an already mature root system: with symbiotic bacteria and fungi present) is recommended. Density aims at stirring competition between species and the onset of phytosociological relations close to what would happen in nature (three to five plants per square metre in the temperate zone, up to five or ten seedlings per square metre in Borneo).