This doesn't surprise me at all, from the late 1960s to the late 1980s Japan has had an obsessive and hyper conformist culture, people who have never lived in Japan for a lengthy period of time will never understand it. During those years of spectacular economic growth there came a price tag nobody really talked about. The extreme pressure for men to perform and compete in the social and corporate world is staggering compared to the West.
The educational system was equally has tough, 24x7 cram schools, exam schools and summer schools combined with high entry standards into the Japanese universities and then the corporations.

The average Japanese salarymen were expected to work 12-14 hour days almost 7 days a week, they were expected to socialize after work with their coworkers(team building) for anywhere from 2-4 hours! They got almost no sleep and worked themselves to exhaustion.

Japan is infamous for it's extraordinarily high suicide rate, especially among corporate workers. They even evolved accommodations to service such an inhuman level of productivity called capsule hotels.

When their economy fell into the tank in the mid 90s many of these "ants" found themselves unemployed and forgotten, the reward for their labor and time was a pink slip. The male children of many of these male corporate wageslaves saw the price their fathers paid and told themselves, "Why?" and they were right to do so, because Japan is still very feudal in many aspects of their society.

Discipline, duty and obedience were drilled into Japanese youth to a level not found in the West except for military boot camps.
You wonder why Japanese youth and anyone under 30 tends to be a bit weird and why they have a technologically advanced but screwed up culture, it's because they've literally burned out their younger generation. The Japanese focus on winning is legendary and they almost came to the point passing the US in gross economic productivity in the 80s.

These so called Herbivore men are in fact the product of this culture and they're rebelling for completely different reasons than their Western MGTOW counterparts. We MGTOWs in the West are a logical reaction to the misandry and militant hyper-feminism of our culture, the Japanese herbivores are a reaction to an ultra high pressure, extremely competitive society of corporate drones. They are not doing the boycott of women for the same reasons we are and they wouldn't understand the conflict we have with feminism, because Japanese feminism is of a completely different form then the militant western model.

Japan will pay a high price for this progressive rot, combined with a declining population(Japanese immigration is notoriously tough and they don't tolerate permanent immigrant enclaves, no Chinatowns/Koreatowns etc) and stagnant economic growth(for the past 15 years).

The US is facing something similar in terms of the end result, declining population(offset by massive illegal immigration and births in that immigrant population) and stagnating economic growth in the foreseeable future. MGTOWs and Herbivores are fellow travelers along the same road but for completely different reasons.