Artist.
Japanese name: タチバナ (Tachibana)
Old names: うたろう (Utarou) or ぺる (Peru)
Judging from the pixiv ID and art style, the page listed below was the artist's old account:
https://www.pixiv.net/users/13080220
https://www.pixiv.net/stacc/digital_selery
https://seiga.nicovideo.jp/user/illust/7750639
https://www.nicovideo.jp/user/7750639
https://sketch.pixiv.net/@digital_selery
https://www.pixiv.net/users/166655
https://www.pixiv.net/users/789107
https://www.pixiv.net/stacc/moon-cat
