What should we do against a trademark registration if we have been using the same name for our product?

Operating out of Singapore, we provide IT consulting and development services to customers all over the world. I would like to ask about a problem of Japanese trademark law.

For about eleven years now we have been offering our products to customers in Japan. We have been using the name of one of our products as a domain name (.jp) and used the name on flyers, marketing materials, public presentations, etc. However, we have never officially registered a trademark for it. We have recently discovered that another company has registered the same name as a trademark in Japan, also for IT consulting services. From what we can tell, the other company has not been using the name before and it is related to a new product.

Is there anything we can do against that competing registered trademark because of our older presence in the Japanese market? Or do we have to fear a lawsuit by the trademark registrar if we continue to use our product's name as a domain name and for our business activities in Japan? Thank you very much for your initial insight!