Akasaka Tadamasa is the founding master of the Akasaka school, a lineage of tsubako who relocated from Kyoto to Akasaka in at the beginning of the period, thereafter flourishing until the end of the shogunate. He is traditionally held to have been active from the 'ei to Meireki eras (1624-1658), bearing the personal name Shozaemon. Together with nidai Tadamasa and Tadatora, Tadamasa constitutes the so-called "Upper Three Generations" (jo ) of Ko-Akasaka, none of whom left confirmed signed works; identification thus depends upon later appraisals (). As iron openwork makers, the Akasaka school is renowned alongside those of Kyoto, Owari, and .
The technical character of Tadamasa's work is firmly established in assessments. His plates exhibit a calm, restrained finish with the rising toward a gentle central height (nakadaka). The connecting bridges of the openwork broaden as they approach the rim, producing an impression of stability, and the rim is customarily finished as a powerful . The often narrows toward the top into an almost pointed form, and the -ana is characteristically smaller than the -ana -- a diagnostic trait shared with the second generation. In forging, many examples employ the composite sanmai-awase lamination, whose striped patterns are sometimes visible on the rim. Subjects include established motifs such as "Hachi-no-ki," "Shiguretei," "Musashino," praying mantis, "wind in bamboo," and interlocking rings, rendered through inventive designs drawn from natural scenery and classical literary precedent ().
The consistently characterizes Tadamasa's production in terms of dignity and refinement. Works are described as "dignified" and "full of spirit and resonance," possessing "refined elegance" and "rustic feeling." The iron forging and patina color are praised as "exceptionally fine," and the interplay of positive and negative openwork (in'-) is noted as "adroit." Among Ko-Akasaka works, the finest examples attributed to the first generation are judged to be of "particularly elevated dignity," representing the earliest and most authoritative phase of a tradition that would endure for nine generations under the Tadatoshi name.