People who get labelled as "freeters" aren't necessarily bouncing from job to job voluntarily. For decades Japanese corporations were labor-heavy because of life-time employment. When the bubble burst, they broke that unspoken promise and shed themselves of thousands of workers.
When things picked up again, instead of returning to that previous promise, they hired temporary workers. No benefits, no annual pay raises or twice a year bonuses, etc. (And no loyalty from these workers)
The Japanese corporate system is set up that you are hired after college at a low salary, but you are guaranteed a steady climb until you can retire comfortably in the end. The corporations pulled the rug out from under that system.
So you now have many young people who have been fully employed at MegaCorp for 3 years, but on a contract basis, never knowing when it will end, never getting a decent raise...
If you read newspaper and magazine articles here you realize there is an enormous sense of insecurity among the 20 to 30 year age group; and so they are unwilling to take risks, get married, buy homes, etc. People are retreating into themselves.
It would make sense that that is linked to minimalism - or at least, a reduced consumerism - but that would only be my own speculation.