How exactly is Mastodon decentralized?
There are different ways in which something can be decentralized; in this case, Mastodon is the "federated" kind. Think e-mail, not BitTorrent. There are different servers (instances), users have an account on one of them, but can interact and follow each other regardless of where their account is.
Recently, the handling of online defamation has become a hot topic on many mass media as well as social media channels. News Article for Reference: https://www.jiji.com/sp/article?k=2020052500387 In response to these reports, it is expected that lawsuits and disclosure requests will become more publicly known; and government agencies will order stricter enforcement in addition to tightening regulations. However, under the current state of Japan, we will not be able to handle the increase of such administrative burdens and will have trouble dealing with it appropriately. Thus, we have decided to stop providing our service on mstdn.jp and mastodon.cloud starting June 30, 2020. We are very sorry for the inconvenience and appreciate your understanding on the matter.