Yes, VPN could be a reason. Some sites block certain countries (geo block) or provider IP ranges.
Another source of trouble could be that somebody else from your IP range misbehaved and the ototoy.jp admins simply blocked the whole range, instead of that single offending IP.
Some services love to block whole ranges in order to prevent bad connections. This is, however, a bad (and lazy) practice, as it blocks regular traffic also.. as we can see here in this case.
So, if VPN is not the cause, you could try to contact ototoy.jp somehow (just in case e-mail is still allowed from your IP range), and tell them that you have trouble visiting their website, what you IP is, e t c.
Sometimes these range blocks are only temporary, like in the case of e-mail (spamhouse/spamcop for instance) or web site traffic.. often being protected by services like Cloudflare.
If attacks from a certain IP range continue, these services will keep the blocking in place. If attacks stop, the bans will most often be lifted after 24 hours.
Cif ~