No ceremony is required under Japanese law. If you are marrying a Japanese national abroad, he or she may need to submit a Certificate of Marriage Qualification "kon-in-yoken-gubi-shomeisho - 婚姻要件具備証明書".
This is available from their regional branch of the Legal Affairs Bureau "地方法務局". Further information is available on the Legal Affairs Bureau website.
As a foreign national living in Japan, if you wish to get married under Japanese law, you will need to register your marriage at a municipal office of the current or legal address of the Japanese spouse’s residence.
At the municipal office, you need to fill out a Marriage Registration "kon-in-todoke - 婚姻届". The registration form is available at your municipal office. The marriage registration must be signed with signatures and Hanko by two adult witnesses.
Along with the registration, a foreign national will need to submit A Certificate of Legal Capacity to Contract Marriage "kon-in-yoken-gubi-shomeisho - 婚姻要件具備証明書". This document is issued by your home country to certify that you meet the requirements to get married under the laws of your home country. The document can be obtained from your embassy.
The general requirements for marriage under Japanese law are: