The Kaidahara Tumulus No. 29 is a scallop-shaped burial mound located near the Kisacho area of Miyoshi City, Hiroshima prefecture. As part of field training for the twenty-fourth annual class of archaeology majors at the Hiroshima University School of Letters, we conducted a topographic survey of the area with the aim of creating a detailed survey map of this mound, and to clarify the ranking of Kaidahara tumulus No. 29. The results of this survey indicated that this tumulus is a scallop-shell kofun burial mound, 29 m in length and was constructed in the middle of the 6th century CE. Additionally, we proposed the hypothesis that this tumulus was constructed using the same mound-building techniques as in the case of the Kaidahara tumulus No. 20. Further, we discovered a trend in the scallop-shaped tumuli of the region upstream of the Basen River, whereby, over time, the size of square shaped mounds grew in relation to the round ones.