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I presume you are an Indian national.
According to the Ministry of Foreign Affairs of Japan in a document which outlines the application procedure for Nationals of India, you can use an Income certificate or bank statement:
1. Eligibility for Applicant
Nationals of India with ordinary MRP (Machine Readable Passport) / e-passport in compliance with the ICAO (International Civil Aviation Organization) standard, who wishes to apply for a Multiple Visa for a stay of up to 30 days and are applicable to one of the following categories:(1) Individual who has travel record as temporary visitor to Japan in the last three years and who has ability to pay the travel expense
(2) Individual who has travel record as temporary visitor to Japan and travel records as temporary visitor to G7 countries (except Japan) in the last three years
(3) Individual with sufficient financial capacity
(4) Spouse or children of the individuals who are mentioned (3) above
2. Necessary Documents to Submit
...
(3) Applicant with sufficient financial capacity (as mentioned 1(3) above)a. Application form (with Photo)
b. Passport (MRP / e-passport in compliance with the ICAO standard only)
c. Documents to prove the sufficient financial ability such as income certificate, bank statement, or income tax return (and some additional documents which certify incomes such as stock dividend, pension, retirement allowance, inheritance, lease agreement, real estate register, deed of property etc.)
d. Applicantβs Certificate of employment
e. A letter of explanation stating the reason of applying for the multiple visa
(f. if applying from outside of India) documents to prove that the applicant legally resides in that country
If you go through the entire document, you should have all that you need to submit an application for a visa. Good luck.