Hoshiai Hasseki (星合八碩, 1669-1693; by other sources: 1666-1692) was a 7 dan (posthumous) pupil of Dosaku. In 1683 he made his first appearance in castle games, becoming the first such player outside of the Four Houses. In 1691 he returned to Ise (due his illness) and there died in 1692.
Hayashi Monnyu - Hoshiai Hasseki B+4 1683-01-17
Hoshiai Hasseki - Hayashi Monnyu W+3 1684-01-05
Yasui Chitetsu - Hoshiai Hasseki B+8 1685-01-20
Hayashi Monnyu - Hoshiai Hasseki B+R 1685-12-25
Inoue Dosa Inseki - Hoshiai Hasseki B+3 1688-01-14
Inoue Dosa Inseki - Hoshiai Hasseki B+5 1690-01-29
He won six of the seven castle games he played. Wikipedia Japanese edition lists a loss in 1688 (by 3 points, playing white) against Inoue Dosa Inseki.
Some games of this prodigy: http://web2go.board19.com/gopro/psnx_list.php?id=517