Since his predecessor domain lord Nagatomi ICHIHASHI had no heir, Nagakazu was adopted by him and succeeded the family on November 16, 1844, when Nagatomi retired.
先代藩主の市橋長富に嗣子が無かったため、その養嗣子となり、弘化元年（1844年）10月7日の長富の隠居により後を継いだ。