Chinese ink maker, Yuyi is a bit of a mystery. (On the Fountain Pen Companion website they are grouped together under the brand Memory Fish, but I don’t have any info to confirm they are the same company.) There are several series of inks sold under the Yuyi brand on popular shopping sites. Most of the inks I have seen offered have been pigmented inks in series themed on art or tropical fish. They are very reasonably priced.