According to official blog,  music composer Ichiko Hashimoto announced that upcoming anime series Code Geass Gaiden: Boukoku no Akito will be a four-episode series OVA.

Each episode will be 50 minutes long which will be released every three months. First episode will premiere this coming summer.

Hashimoto is the singer behind the music of the said Code Geass spin-off.

Synopsis
The story takes place in Europe in the year a.t.b. 2017. A Knightmare unit made of boys and girls from Zone Eleven are thrown into a military operation with a 5% chance of survival. They must rescue an allied unit left behind on the European warfront. [MAL]

Trailer

[Source]