ei_(pakirapakira) -> jin_young-in.
Reason: Artist uses 永仁 on Pixiv, but apparently this is hanja for his or her Korean name, given on the website as
Young-in / 영인
The artist has the Twitter handle jinyoungin, and Jin seems to be a legitimate Korean family name, though I only see the romanized proof there (doesn't seem to be written anywhere in hanja or hangul on the website).