Maybe it's just culture differences, but the article is about a 30 year old man who lived with his parents, yet the whole time the article refers to him as their [his parents'] son, with examples of how the parents are treating him as a child (or at least a late teen).
If the family had consulted me, I would have first asked that they promptly commit to a policy of zero-tolerance against violence, and to set a maximum limit on their son's allowance. The family had entrusted the son with management of the parents' salaries ostensibly to teach him about autonomy. They also allowed the son free use of credit cards, which led to piling debts.
The most important thing in such a situation is to maintain a certain limit on the son's monthly allowance even if he shows strong resistance. Credit cards are out of the question. Stand firmly by these rules, and if violence erupts, respond by calling the police and escaping to a safe place.
How on earth is a 30 year old man going to be "taught autonomy" by other people giving him their money and a monthly allowance? Kick him out of the house and stop treating him like a child if you want him to grow up.
The whole article seems a little bit "off" since it gives three examples in Japan where adults
have murdered others, yet the article refers to these adults (except the first one) as children.
Like I said, maybe it's a cultural thing, but I can hardly take anything the article says as good, sound information when it constantly refers to adults around the age of 30 as children.