It was announced on the official site, as well as at the end of the final TV episode, that Volume 7 of Sekai Seifuku: Bouryaku no Zvezda, which will be released on October 15, 2014, will include the unaired episode 13. The episode's title is "Shin Zvezda Daisakusen (New Big Zvezda Operation)."
I've always... always been watching you... This whole time... Because you were there... That's why I was able to try hard. So you could have some balance! So you wouldn't treat me like a kid! So you would see me as an actual girl! Even while you were gone... You were right here! You were right here in my heart!