Dadachamame is the common name for edamame soybean [Glycine max L.(Merr.)] cultivars, ‘Shirayama’, ‘Kanro’ and ‘Oura’, which have been established in Tsuruoka city, Yamagata prefecture in northern Japan since the late Edo era. Dadachamame has a good taste and special aroma. Although it is known that the good taste of Dadachamame is caused by the higher levels of sucrose and free amino acids based on the comparative analysis of chemical components in the seeds of Dadachamame and other soybean cultivars, details on the genetic level are unclear. To understand the good taste of Dadachamame on the genetic level, in this study, we developed an F₂ population derived from a cross between the Dadachamame cultivar ‘Shirayama’ and the soybean cultivar ‘Enrei’. In the early development stage, Shirayama seeds had about 2-fold higher accumulation levels of sucrose compared with Enrei seeds. Sucrose content and genotype of the F₂ population suggested that the quantitative trait locus (QTL) for high sucrose accumulation is located on the long arm of chromosome 12. The genes responsible for determining the sweetness of Shirayama may be present on chromosome 12. Using the lines developed from crosses between Dadachamame and soybean cultivars in future studies, we will attempt to identify the genes responsible for QTL that control for the good taste in specific Dadachamame seeds, and discuss the mechanisms for determining the good taste of Dadachamame to improve the palatability of edamame. Furthermore, we have developed mutant edamame populations that can be used for edamame breeding. Since mutant soybean populations have already been developed, meticulous soybean breeding will be possible in the future for creating the desired characteristics for the final soybean products.