Raku IV Ichinyu (1640-1696)
楽四代 一入

Ichinyu was born the eldest son of Raku III Donyu (1599-1656). Upon the death of his father, he became his successor at the young age of 17. Ichinyu was one of the teachers of both Honami Koho (Kochusai, 1601-1682; Honami Koetsu's grandson) and Ogata Kenzan. Most prominent of all potters having been Ichinyu's studends is Chozaemon (1630-1713), the founder of the Ohi kiln in Kanazawa.

References:
Signature and seal of Ichinyu, see: Encyclopaedia of Signatures and Seals (落款花押大辞典 Rakkan Kao Daijiten), Kyoto 1982, p. 1432