According to OCN news, the first episode Code Geass Gaiden: Boukoku no Akito will be shown at ten theaters in early this summer. Sudo Tadashi, the president of Anime!Anime!, reported that there will be more than one episode of Akito anime. The story of Akito takes place in the same period as Lelouch's. There will be an interaction in the story between the two anime.

Trailer of Akito (Youtube)
Akito official website

Cast
Akito: Irino, Miyu
Layla: Sakamoto Maaya

Theme Song Singer: Sakamoto Maaya
Theme Song Composer: Kanno Yoko

The cast of a musical stage of Code Geass was also announced. The actors are all male even for the female characters.

Code Geass Musical official website

Cast
Lelouch: Takagi Shinpei
Rolo: Futa
Suzaku: Nakatsuka Kohei
C.C.: Akaba Mio
Karen: Wada Taisuke
Euphemia: Mikami Shun

Sources: OCN, Sudo Tadashi's tweet