Seiya Kaihatsu (Japanese: 開發 聖也, Hepburn: Kaihatsu Seiya; born July 30, 1987) professionally known as Seikin (Japanese: セイキン), is a Japanese YouTuber and singer-songwriter. His younger brother is YouTuber Hikakin, who is also a member of the Japanese music group Hikakin & Seikin.
Source: “Seikin”, English Wikipedia (CC BY-SA 4.0), excerpt