That makes up about 338,000 people across the country, with 40% beginning their isolation in adolescence, according to the ministry.
Various factors are thought to be at play, including financial hardship, mental illness, family problems or health challenges.
The report also detailed future plans for further action, such as distributing guidelines to local governments, boosting youth social safety nets and early detection systems, and working more closely with youth welfare facilities like shelters or rehabilitation centers.
Japan has a similar problem, with nearly 1.5 million reclusive lonely young people, who are known as hikikomori, according to a recent government survey.
Of those surveyed, more than a fifth cited the pandemic as a significant factor in their reclusive lifestyle.