Pilot iroshizuku Fountain Pen Ink Cartridge - Tsuki-yo

Pilot Iroshizuku Fountain Pen Ink Cartridges — Tsuki-yo (Moonlight)

Tsuki-yo means moonlight in Japanese, and this ink earns the name. It is a deep, composed blue with a quiet teal undercurrent — the colour of a night sky over still water, lit not by daylight but by something softer and more considered. On quality paper, those paying close attention will catch a faint red sheen at the edges of broader strokes. It is not a showy ink. It rewards attention.

This is Pilot's celebrated Iroshizuku line in cartridge form. Since its debut in 2007, Iroshizuku has built a devoted following among serious fountain pen users for its consistent flow, vibrant saturation, and the care that goes into each colour. Tsuki-yosits comfortably in that tradition: professional enough for daily correspondence, characterful enough to make writing feel deliberate.

Each box contains six proprietary Pilot ink cartridges, each holding approximately 0.8 ml of ink. The cartridges are compatible with Pilot and Namiki fountain pens that accept the Pilot proprietary cartridge format, including the Vanishing Point, Custom 74, Metropolitan, and Explorer, among others. Each cartridge is individually printed with the ink name, a small but considered touch that reflects the attention to detail Pilot brings to the Iroshizuku range.

The packaging itself is worth noting. It follows the aesthetic of the iconic blown-glass Iroshizuku bottle, with a sliding inner tray and an internal latch that prevents the tray from pulling completely free. It presents well. The cartridges are made in Japan.

For those who already use Tsuki-yofrom the bottle, the cartridges offer a genuine convenience, particularly for travel or for a dedicated pen that you want to keep inked with a specific colour without the fuss of a converter. For those new to the colour, this is an accessible way to try one of the more beloved blues in the Iroshizuku catalogue before committing to a bottle.

The ink performs well across medium and broad nibs, with a wet, smooth flow and a dry time of approximately 30 seconds on quality coated papers. On standard copy paper, some feathering is possible, as is the case with most high-flow inks. It shades gently across different paper weights and performs best on fountain pen-friendly surfaces like Rhodia and MD Paper.

Compatibility: Pilot and Namiki proprietary cartridge fountain pens, including Vanishing Point, Custom 74, Custom 912, Metropolitan, Cavalier, and Explorer.

Contents: 6 cartridges x 0.8 ml per cartridge