Resumen: <p>Japan and Spain represent different cultural contexts and educational practices that could influence the way students approach mathematical concepts. To understand the differences in approaches to number sense in mathematics learning opportunities within the textbook between Japan and Spain, we compare the arithmetic section of the first year of primary school in the official Japanese textbook and in the textbook published by the top-selling publisher in Spain. Through qualitative analysis, the meaning of numbers, general aspects reviewed in the literature, and representation registers were analyzed. Among the results obtained, we found a key distinction between the two countries in the emphasis they place on the different mathematical operations. In addition, the introduction of number operations also differs. For example, the Spanish textbook usually presents systematic counting tasks together with number writing and then gradually integrates the basic operations, while the Japanese textbook emphasizes the understanding of mathematical concepts by breaking numbers into smaller parts and introducing the ideas step by step. Finally, the similarities are also remarkable. Both textbooks predominantly use symbolic representation, demonstrating a common reliance on numerical symbols in the early teaching of arithmetic.</p> Idioma: Inglés DOI: 10.18848/2327-7971/CGP/A211 Año: 2026 Publicado en: International Journal of Science, Mathematics and Technology Learning (2026), [31 pp.] ISSN: 2327-7971 Financiación: info:eu-repo/grantAgreement/ES/DGA/S60-23R Tipo y forma: Artículo (Versión definitiva) Área (Departamento): Área Didáctica Matemática (Dpto. Matemáticas)