No its done by a Tatsuki fan who explicitly rejects anything outside of Tatsuki's work. His Pixiv is here https://www.pixiv.net/member.php?id=321750 And his story summery is: This is the story of the + i story world line, depicting the continuation of the journey of the “world of irodori”. * The creator is a fan of irodori and the world of irodori's "only".