Chōsokabe Yasutoyo served as a bushō during the early Edo period.

Around 1599, Yasutoyo was born as the sixth and youngest son of Chōsokabe Motochika, a sengoku daimyō of Tosa Province and the twenty-first head of the clan.  Following the demise of the Chōsokabe clan, during the Siege of Ōsaka, Yasutoyo followed his older brother, Chōsokabe Morichika, but, after the fall of Ōsaka Castle, he fled.  Later, he adopted the name of Adachi Shichizaemon and served Sakai Tadatoshi for a stipend of 1,500 koku.  His descendants became senior retainers with a fief of 5,000 koku.

While Yasutoyo was headed toward Kawagoe in the Iruma District of Musashi Province, he stole a kimono from a farmhouse in Yamashina and, intending to rely upon connections in Utsunomiya, intended to head east.  However, without having eaten for two days, he spent a night at the Taga Shrine in Shinano.  He then pretended to be a fortune teller under the name of Abe Yasutoyo, a descendant of Abe no Seimei, a diviner from the Heian period in the early eleventh century.  Using his quick wits, he deceived local villagers and resolved the incident regarding the theft, earned ten ryō, and headed east.  Yasutoyo then resided in the Chōkō Temple in Sunpu and, using the surname of his mother, adopted the name of Adachi Shichizaemon.

One day, when Sakai Tadatoshi, the lord of Sunpu Castle, was engaged in a falconry outing, a person who had gone mad attacked Tadatoshi with a sword.  As a neighboring resident of Tadatoshi, Yasutoyo had been assisting with the outing, and he stopped the assailant.  Tadatoshi then inquired as to whether Yasutoyo was simply a farmer, whereupon Yasutoyo revealed his background.  Surprised at the revelation, Tadatoshi granted Yasutoyo 500 koku and promoted him to the status of a retainer.  Thereafter, his fief was increased to 1,500 koku.