Torakazu did not actually change his surname to Doi until his marriage to Sugino DOI, a student at Tohoku University who translated Anna SEWELL's "Black Beauty: the Autobiography of a Horse" under a phoneticized version of her own name, Sugino DOI.
結婚して虎賀壽は土井姓になったが、妻の土井杉野は、元東北大に学んだ学徒で、土井すぎのの名でアンナ・シュウエル『黒馬物語』の翻訳がある。