URLs

• https://twitter.com/oka_yu_1
• https://twitter.com/intent/user?user_id=299563377
• http://okayudou.blog.fc2.com
• http://doujinshi.mugimugi.org/browse/author/79545/Oka-Yuuichi/
• https://anidb.net/creator/9087
• https://www.animenewsnetwork.com/encyclopedia/people.php?id=41259
• http://www7.atwiki.jp/anime_wiki/pages/1370.html
• http://www18.atwiki.jp/sakuga/pages/64.html
• http://okayudou.com