What to wear for first day of work in Japan?

Hi guys I’m starting work in a foreign company in Japan, specifically in the banking and finance industry. Based on where I come from generally we tend to wear whatever we like to work and I’ve never worn a suit before for work. However I heard that in Japan it is kind of considered necessary to wear a suit on the first couple days of work. Is this true? I’m wondering how to dress appropriately yet not be too overdressed especially considering the extreme summer heat now.