The Pen Itself
The Pilot Futayaku is a twin tipped brush pen that features two colors- black and grey. Both ends have the same size nib. The grey end has a transparent cap, while the black end has an opaque black cap, so as long as you post the cap correctly to the end, you should have no issue telling which end is which. Just to make sure there's no confusion, the ends are marked on the plastic barrel of the pen itself.
There's an ink indicator for both shades on the side of the barrel, which lets you know when you're running low.
Both caps are capable of posting to one another, which is pretty handy, as it helps prevent your cap from rolling off the desk and disappearing forever. Only the black end features a clip.
Both tips seem to be of the same quality.
And the brush strokes are uniform, regardless of the ink color. When the grey ink is applied directly after the black ink is applied, it causes the black ink to smear. I've covered ways to handle this in the past, but honestly, this isn't the best pen for fills or shading anyway.
The Field Test
This pen handles well, has two fairly responsive tips, and is fun enough to ink with.
Fude pens that offer two colors in one are a great space saving alternative to carrying both gray and black fude pens in your pencil case. While the Pilot Futayaku isn't remarkable, it isn't a bad pen by any stretch, nor is it overpriced, as it's only $3.30 on Jetpens. When writing this review, I had some difficultly finding things to say, because the Futayaku isn't really all that different from other double sided grey and black fude pens available, it neither fails nor excels.