If you've come across sync.fout.jp and are wondering whether it's safe, the short answer is: we can't recommend it. The site is completely locked down — it returns a 403 Forbidden error to anyone trying to visit. That alone makes it impossible to judge what kind of business or service is behind it.
More concerning is that the domain registration itself is hidden. The WHOIS database returned no match, which means either the domain isn't properly registered or the owner is deliberately concealing their identity. Legitimate businesses, even private ones, typically have some traceable ownership. The site also blocks all search engine crawlers and has no presence in the Wayback Machine, so there's no history to check.
For a site that offers no public face, no way to contact anyone, and no visible purpose, the safest approach is to assume it's not meant for ordinary users. If you were considering using sync.fout.jp for anything — syncing files, data, or accounts — hold off until there's real evidence of who runs it and what it does. The lack of transparency here is a serious red flag, and our sync.fout.jp review rates it as Suspicious.