I am Bangladeshi. I live in Italy. I have a 5 years permesso di soggiorno, 10 year's residence ID card, tessera sanitaria and codice fiscale from Italy.
I want to go Japan to meet my friend who lives there. Do I need a visa to enter Japan and can you give me some information about what I need to apply?
A national of Bangladesh needs a visa to visit Japan. There is no exception for being a resident in Italy.
You can find instructions to apply for a visa on Japan's Ministry of Foreign Affairs web site. After you fill out the application and gather the required documents, you need to deliver them (they say via fax or e-mail) to the embassy/consulate serving the region of Italy you live in. The Japanese Embassy in Italy web site has more information (in Italian).
Aside from the previous answer, if you are visiting a friend or staying at their place, make sure to mention it to the embassy as you will definitely be asked this upon arrival. In Japan, you will be asked to fill in an immigration form which will include information such as purpose of visit, place of visit and similar. Additionally, you'll also fill in a custom's declaration at the customs. Be mindful that if you notify the embassy that you'll be visiting a friend, in some cases they may request a guarantee or invitation letter from the person you're visiting but this may be a case-by-case thing and it's better to check it with the embassy itself :)
