Yokoya Somin was born in in 10 (1670) under the personal name Tomotsune, and the published sources call him the third-generation master of the Yokoya family, the largest school of metalwork. His grandfather, the first-generation Soyo, had studied with the Goto house and served the shogunate as an official metalworker. Somin likewise entered shogunal service and trained in the hereditary iebori manner. Then, finding the convention-bound idiom of the Goto house unsatisfying and "influenced as well by the tastes of the time," he gave up his stipend and worked independently. There he "exercised his abilities to the fullest, achieved great success, and came to be called the founder of ." He used the common name Chojiro, later Jihei, and the art name Ton'an, and died in Kyoho 18 (1733) at sixty-four.
The published sources tie his designs to the painters of his day. He was on close terms with Kano Tan'yu and with the Kano-trained Hanabusa Itcho, used their under-drawings in his work, and from them developed his own Yokoya lion and his branches of peony. such as the Asazuma boat are thought to follow Itcho's designs, and the lion's posture is described as the Yokoya lion formed under Itcho's influence. This basis in contemporary painting is what separated his carving from the formal repertoire of the Goto.
Somin's manner "may broadly be divided into two principal modes": richly modelled with polychrome inlay () in gold, silver and , and , "a technique he originated." In the first, the published sources praise the abundance of modelling and the play of high and low, joined to a free and open chisel, as showing the bearing of a king, 「圧倒的な肉置きの豊かさと高低の変化は自由闊達な鏨捌きと相俟って、正に王者の風格を堂々とあらわしている」. His on , his polished , and the , and he used beside them show a command of the whole Goto-derived craft. In the second mode his chisel shows "pronounced modulation" and "decisive" strokes, "alternating depth and shallowness at will," with "modulations of speed and emphasis that recall ink painting."
Among his own creations are the Yokoya lions, rendered with such immediacy that "one experiences the illusion that the lion might spring forth from the ." Another is the vertical tatezu composition for , depicting lions, tigers, horses and other subjects "from the front or from behind," which the published sources, in sixteen of his records, call novel and of great influence on later metalworkers. He also harmonized contrasting finishes and carving methods within one piece: on a of Fukurokuju the high relief of the front and the of the back are brought together, a task the published sources call "an exceptionally difficult" one. His are carved with a thin modelling and in'-ne roots, features the published sources note as points of appraisal.
The published sources sum up his work as showing 「横谷一門の統帥としての貫禄と抜群の技術」, the authority of the head of the Yokoya school and outstanding technique. They hold that it stands comparison with the work of the Goto main house, and that his Goto origin and thorough training show plainly in its dignity. Of his lions they repeatedly write that 「他工の追随を許さない厳しさと凄味がある」, a severity and awe-inspiring force other craftsmen could not rival. They credit him with having "opened a new direction through freer, life-sketch-based realism."
Somin's designated record is the strongest of any artist in the database by designation factor. He has no National Treasures, but four of his sets are Important Cultural Properties, among them a and of lion and peony; six works are and twenty-five . The Important Cultural Properties are heritage held in trust rather than pieces that trade. His pieces descend through and collecting houses. The recorded provenance includes the Hosokawa, among them Hosokawa Moritatsu and the Eisei Bunko collection, the Tsugaru, the Shimazu, the Arima and the Sakai of Shonai. No current institutional holder is recorded against the designated pieces. His signed and at the and ranks come to light only rarely, each a document of the moment when metalwork left the Goto conventions for the freer manner he founded.
