In the Tenchi Universe continuity, Achika Masaki is the mother of Tenchi Masaki. Her parents are Katsuhito and Itsuki Masaki.

Achika plays a major role in Tenchi in Love. The Tenchi gang travel back in time to save Achika from the extradimensional being Kain.

Tragically, Achika dies when Tenchi is young. While we are not shown these events, episode 9 (No Need for Memories) shows some flashbacks to scenes following her death.

Achika should not be confused with Kiyone Masaki, Tenchi's mother in the OVA series.