Yes, this is gluten free
Not wheat, despite the name. Buckwheat is a seed related to rhubarb and sorrel and is naturally gluten-free — but soba noodles made from it are usually blended with wheat flour.
A seed, and not a cereal at all. Buckwheat is Fagopyrum esculentum, a member of the knotweed family, which makes its closest food relatives rhubarb and sorrel — not wheat, not barley, not any grass. The edible part is a small three-sided seed. Hulled it is a groat; roasted it is kasha; milled it is the dark flecked flour behind blini, galettes and soba.
Because of eight letters that mean nothing. The name is a translation accident — Dutch boekweit, beech wheat, for a seed shaped like a beech nut and used the way wheat was used. Nothing botanical connects them. It also trips every piece of software that checks ingredient names for the substring "wheat", which is how buckwheat ends up flagged by scanners and quietly avoided by people who did nothing wrong.
Soba is the entire risk and it is a large one. Most soba sold anywhere is a blend, often majority wheat flour, because buckwheat has no gluten and is difficult to work alone. The styles are named: juwari soba is a hundred per cent buckwheat, ni-hachi is eighty per cent buckwheat and twenty per cent wheat. Only juwari is yours, and in a restaurant it is also being boiled in water that has cooked the other kind. Beyond soba, buckwheat flour is frequently milled on shared equipment, and uncertified specialty flours test positive often enough that certification is worth paying for here.
This entry exists so that CiCi does not make the mistake the software usually makes. Buckwheat returns gluten-free on its own, while soba is treated as a product to check rather than a buckwheat question answered.
Every one of these is the same ingredient. The number of names is a large part of why gluten slips past people who read every label.
Point CiCi at the barcode on the product you're holding and get this same reasoning in about two seconds, plus the carbs and the full nutrition panel. 360,000+ packaged foods are already read and waiting.
The aisle guides below cover Buckwheat in context — which is usually the more useful question, because an ingredient rarely appears alone.
This answer comes from CiCi's ingredient lexicon — the same rules the scanner uses, not a separate article. Where reputable sources disagree, CiCi takes the conservative position and says so.