Esterbrook x Bungubox SD Kachu Fugetsu Kingfisher Review: A Fountain Pen That Captures a Bird in Flight

Introduction

Some pens earn their place in a collection through sheer practicality. Others win you over the moment you see them in the light. The Esterbrook x Bungubox SD Kachu Fugetsu Kingfisher is firmly in the second camp. This limited collaboration between Esterbrook and the Japanese stationer Bungubox is a themed, nature-inspired offering built around the kingfisher, and it is one of those pens people tend to buy on impulse after seeing it in person.

Availability is limited. Units are still listed through the Bungubox website, but stocks are thinning and the pen is not expected to remain widely available for long. If the visuals speak to you, it is worth checking current availability soon.

Unboxing and First Impressions

The pen arrives in a custom box that slips open to reveal information about the pen, a cartridge, and a small envelope containing a QR code to activate the pen. The envelope is a charming touch, and the custom box itself is nice enough that many owners will hesitate to throw it away.

Bungubox has a strong track record with special editions, hitting the mark with a high percentage of its collaborations. This release follows that pattern, and the packaging sets the tone before you even reach the pen.

Design and Materials

The material is made by McKenzie Penworks and is their diamond cast material, infused with actual diamond dust. Tiny flakes in the resin give the pen depth, shimmer, and luminosity. Inspired by the kingfisher, a migratory bird that arrives in Japan each spring and leaves in autumn, the material captures the green, blue, and orange of the bird’s plumage along with the iridescence that shifts color depending on light and viewing angle. It does a genuinely excellent job of capturing that theme.

Because this is a custom material, every rod is unique, so no two pens will look exactly alike.

Build and Features

The SD is a cartridge converter pen that accepts standard international cartridges, and a converter is included. A nice detail: the converter features small kingfisher illustrations that remain visible even when the pen is inked up.

Trim is gold, and while some prefer silver, gold works well with these particular colors. The barrel is engraved with both Esterbrook and Bungubox, with the Bungubox branding in its own font. The cap twists off with one and a half rotations, and the inner cap is spring loaded, which gives it a slight bounce. You need to apply a little pressure when capping and anticipate the release when uncapping, though the cap will not fly off. The tighter connection helps keep the nib from drying out.

The section is not overly long, so grips may rest on the threads, but the threads are smooth enough that this does not cause discomfort. The cap posts, though not deeply, and it is light enough not to backweight the pen. It does give the pen a slightly mushroom-shaped look when posted, so many users will prefer it unposted, where it is plenty long enough.

Nib Options and Writing Performance

The nib is a stainless steel size six unit available in extra fine, fine, medium, broad, or a 1.1 stub. The review unit ran a broad nib, which proved very wet and juicy, laying down a generous amount of ink. Reverse writing is fairly smooth and produces a nice medium line, and fast writing is decently smooth with just a hint of feedback. The feed keeps up nicely throughout.

Pairing a broad nib with Bungubox 4B ink, a popular blue black, makes for a pleasant writing experience overall.

Pricing and Availability

Pricing varies by retailer. Purchased through Yoseka Stationery in New York, this example was $315. The Bungubox website lists it at approximately $380 depending on currency conversion rates. Ordering internationally raises questions about taxes, tariffs, and shipping that are harder to predict right now, so factor that into your decision. Yoseka Stationery itself is worth a visit if you are ever in New York City: a short walk from the Manhattan to Brooklyn ferry dock, with a great selection of pens and stationery.

Measurements and Size Comparisons

Next to other Esterbrook models, the standard SD sits between the smaller pocket-sized Niblett and the oversized SD Raven. Compared against non-Esterbrook pens like the Montegrappa Elmo 2, the Twsbi Vac 700R Iris, and the Lamy Safari, it reads as a comfortably sized full-length pen rather than an oversized statement piece.

Buying Advice

This pen makes the most sense for collectors and enthusiasts who respond to themed materials and limited collaborations. If you already enjoy the SD model, this version’s diamond cast resin is arguably the best argument for adding another. If you prefer utilitarian daily writers at lower prices, the limited availability and premium pricing may not justify the purchase on function alone.

For those who do buy, the nib choice matters: the broad nib tested here was wet and pleasant, but five sizes are available to match your handwriting style.

Conclusion

The Esterbrook x Bungubox SD Kachu Fugetsu Kingfisher succeeds because the material delivers on its inspiration. The kingfisher’s greens, blues, oranges, and iridescent sheen come through convincingly, the diamond dust adds real depth, and the writing experience with the right nib is genuinely pleasant. With limited stock remaining, it is a pen to act on if it appeals, rather than one to deliberate over for months.