Saturday, the Star Trek star toured the Fresno fairgrounds, which served as a temporary detention facility for Japanese Americans during World War II.
Takei is in Fresno to attend an opera performance benefiting the Fresno Assembly Memorial Sunday.
The group is working to build a memorial at the fairgrounds to both honor former internees and also educate people about the injustice they endured.
"This Fresno Assembly Center Memorial is another symbol of that -- the determination of the Japanese community that their experience, the failure of the American democracy -- does not go unknown," George Takei said.
Sunday's performance of "The Sisters Of Manzanar" begins at 2 p.m.
After the show, Takei will participate in a discussion, which will include the opera's composer.