My thanks to Glenn for the ink sample.
Kyo No Oto not to be confused with Kyo Iro are both sold by Tag Stationary. Kyo no Oto is a series of 5 inks and Koke Iro is one of them. It’s a yellow-green ink that shades really well. It goes from a yellow-green that’s similar to Pilot Iroshizuku Chiku Rin to a dark yellow-green similar to Rohrer and Klinger Alt-Goldgrün. Yellow-green is my kind of green. I really love Koke Iro though it’s colour isn’t all that unique. It’s shading is really quite something.