The following is from the document you posted, not sure they will all apply though, just posting here for interest....
Article 252. (Embezzlement)
(1) A person who embezzles property in his/her possession which belongs to another, shall be punished by imprisonment with work for not more than 5 years.
(2) The same shall apply to a person who embezzles his/her own property when the person has been ordered by a public office to hold the property in custody
Article 235. (Theft)
A person who steals the property of another commits the crime of theft and shall be punished by imprisonment with work for not more than 10 years or a fine of not more than 500,000 yen.
Article 246-2. (Computer Fraud)
In addition to the provisions of Article 246, a person who obtains or causes another to obtain a profit by creating a false electromagnetic record relating to acquisition, loss or alteration of property rights by inputting false data or giving unauthorized commands to a computer utilized for the business of another, or by putting a false electromagnetic record relating to acquisition, loss or alteration of property rights into use for the administration of the matters of another shall be punished by imprisonment with work for not more than 10 years.
Most countries give you a reduced sentence for pleading guilty, and the chance for further reductions in your sentence for good behavior inside. Sometimes criminals get released on parole half way through their sentence. I don't know if Japan uses that system, but if it does he might only serve a few years if he's found guilty. Remember Nick Leeson, the derivatives broker whose fraudulent trading lost Barings Bank $1.4 billion. He was only sentenced to six and a half years, and he got out early.