The * starred restaurants * are the ones I recommend :D
I've also been to Daikokuya and Shinsengumi, but wasn't that impressed :\ but.... I'll definitely give them another try and also take some photo evidence hehe.
Ajisen Ramen (Rowland Heights)
Cafe Miso (Chino Hills)
* Kairakutei (Tustin) *
Naga Naga Ramen (Pasadena - CLOSED)
* Tayama (Hacienda Heights) *