It should be noted that if you're anime-only, it is impossible to watch this in order. It fits between Pseudo-Singularity IV: Salem, which does not have an anime, and Lostbelt 1: Anastasia, which also does not have an anime. If you actually want the story leading up to this, play the gacha, it's available in English. (Though I'm told the Babylonia (Singularity 7) anime isn't half bad if you ignore the camera's butt obsession and a subpar final boss fight.) Moonlight/Lostroom is a beautifully directed and animated character study of Ritsuka and Olga Marie. There's not much of a plot to speak of besides this, butit's well worth your time. And again, DO NOT WATCH IT unless you have finished Arc 1 of the game's main story, and preferably Arc 1.5 (though I note that you can completely skip the Agartha Pseudo-Singularity - and should, because it sucks).