The World of Numbers: From Natural to Real, Complex, and Quaternions

Free tracked shipping on every order to the US, Canada, the UK, Europe, Australia and New Zealand — and adding more items never costs extra shipping. Orders are dispatched within 1–3 business days of availability (some items are sourced in Japan after you order), and most arrive within 4–12 business days of your order, depending on destination. Some items ship from our U.S. fulfillment partner. For U.S. orders, import duties and taxes are collected at checkout, so there is nothing to pay on delivery.

Every item is genuine and sourced in Japan. Items are new unless the title says used. For books, we show the ISBN so you can confirm the exact edition.

Returns are accepted within 30 days of delivery. If an item arrives damaged, defective, or not as described, we pay for the return or refund you in full; for other returns, the customer pays the return shipping. Opened food and beverages and opened personal care products cannot be returned unless they arrived damaged, defective, or incorrect. See our Refund Policy for full details.