Sangaku (算額), votive tablets with mathematical content, are a cultural heritage unique to Japan. The Sangaku Archive Project, a 3-year initiative based at the Waseda Institute for Advanced Study (WIAS) is an effort to document as many of ca 900 extant sangaku and of ca 1500 sangaku documented in literature in an open-access digital archive (see sangaku-archive.org). The project includes a considerable amount of data collection whereby sangaku need to be visited in their current location (usually a temple or a shrine), photographed and documented in situ. Whilst the majority of the data collection for the Sangaku Archive Project was conducted in AY2024 and the first half of AY2025, a considerable number of sangaku were documented in the second half of AY2025, partially financed by the Tokutei Kadai.

Specifically, the funding received from Tokutei Kadai was used to buy a high-quality camera, and to contributed to the financing of two research trips of ca. 10 days each to document sangaku in various locations and participate in a conference. The first research trip was conducted in Kyushu in December 2025, visiting shrines in Oita, Kita-Kyushu, Fukuoka City and Saga to document the sangaku there, and participate in the 2025 Jinmonkom Symposium in Kyushu University.

The second trip was conducted in Tohoku to investigate several sangaku in Naraha Town and Shinchi Town (Fukushima), as well as Yurihonjo (Akita) and a votive tablet containing a calendar held at Hachinohe City Museum (Aomori).

During the funding period, I presented the Sangaku Archive Project at a symposium organized by IPSJ (Information Processing Society, Japan) in Ishigaki and published a paper in the WIAS Bulletin.