Lord of Damine Castle in Mikawa Province and fifth head of the Damine Suganuma clan. In May 1575, when Takeda Katsuyori retreated after his defeat at the Battle of Nagashino, he sought refuge at Damine Castle, but Sadatada's kinsman Suganuma Sadanao and elder Imaizumi Dozen, left in charge of the castle, refused him entry, leaving Katsuyori stranded. Resentful over this affair, Sadatada in July 1576 launched a surprise attack on his own castle, reportedly slaughtering 96 kinsmen and retainers inside, then capturing Sadanao and Dozen and having them executed by the saw (nokobiki). He was killed in battle against Makino Yasunari in 1582.

Combined loyalty to his Takeda allegiance with fierce resentment over being denied entry to his own castle, and is remembered for the brutality with which he purged even his own kin.

The "Damine Castle tragedy" is passed down as an episode illustrating the brutality of intra-clan strife in the Sengoku period, and reconstructed buildings now stand at the Damine Castle site in Shitara, Aichi Prefecture, conveying this history.