Ishida Bungu is a stationary store based in Hakodate, Hokkaido (Northern Japan). I came to learn of their inks only very recently via discussions of Hakodate Twighlight ad Gagome on the pen forums. You can buy Ishida Bunga inks at http://www.ishidabungu.co.jp/index.php?id=45via the White Rabbit Express service. They do not ship outside of Japan.
In pursuit of my bottle of Pen & Message Cigar in the Winter/Spring of 2017, I decided to get the other 6 colours in the P&M set, as well as 4 inks from Ishida Bungu stationary store, namely; Hakodate Twighlight, Curry, Gagome (Brown Algae) and Old School Brown. My thinking being if I spread the cost of shipping over more bottles of ink I’ll actually be saving money(!).