Also known as: Ikeda Katsushige, Ikeda Shigenari, Araki Kyuuzaemon

Ikeda Tomomasa was the eldest son of Ikeda Nagamasa of Settsu Province, but his father chose another son, Ikeda Katsumasa, to succeed as clan head upon his death due to his superior accomplishments in literary and military arts. Other accounts claim that Tomomasa was an illegitimate son.

Tomomasa plotted with a retainer of the clan, Araki Murashige, to overthrow Katsumasa and send him into exile. He then assumed the position of clan head. Araki later abandoned the Ikeda Clan to serve Oda Nobunaga. Tomomasa allied himself with an enemy of the Oda and was driven into exile. Araki took the opportunity to seize control of the Ikeda Clan. Tomomasa eventually surrendered to Oda, who made him a retainer of Araki Murashige.

When Araki rebelled against Oda and escaped to Amagasaki Castle he entrusted Arioka Castle to Tomomasa and the other retainers, who surrendered the castle to Oda upon his pledge that no harm would befall their wives and children "if Amagasaki Castle and Hanakuma Castle were surrendered to me." Tomomasa and others rode for Amagasaki in order to persuade Araki to surrender, but he refused to receive them. Tomomasa et. al. took flight instead of returning to Arioka Castle, abandoning their families. Oda ordered all hostages to be executed to make an example of them.