Ikeda Yaemon is the 18th head of the Ikeda Clan and also the adoptive brother of Ikeda Asaemon.
As a child, Yaemon aspired to become the next head of the Ikeda Clan. To prove his worthiness for the title, he killed several prisoners, claiming he had performed "Kimoarai" (Soul Cleansing) on them. His father attempted to punish him for this act, but Asaemon intervened. This incident resulted in Asaemon being given the title "17th Ikeda Yaemon" instead of him.
In his final moments, Yaemon killed the Hitotsubashi guards to allow his sister to escape, believing she would restore the clan's honor. For his actions, he was beheaded by Hitotsubashi Nobu Nobu. His body was thrown into the river and could not be recovered by the Shinsengumi.
(Source: Gintama Wikia)
