Saizo Kani was born in Mino Province, serving the Saito clan initially, until the defeat at the Battle of Mt. Inaba Castle in 1561. After then, he served the Oda clan, and fought at the Battle of Yamazaki against the Mori clan, and also fought at the Battle of Komaki-Nagakute in 1584. After that battle, he served as a Toyotomi vassal when Ieyasu Tokugawa, who he served after Nobunaga Oda's death, and fought at the Fall of Odawara in 1590 against the Hojo. After the death of Hideyoshi, he took part in the Siege of Kyoto with his new master, Masanori Fukushima, who gathered a coalition of Anti-Ishida Toyotomi generals and vassals. After the defeat there he joined the Tokugawa again, alongside Masanori, and served alongside him in the Battle of Sekigahara in 1600, where he stuffed severed heads of his enemies with bamboo leaves to mark his kills, and moved to Hiroshima with Masanori Fukushima in 1613, where he died.