This is my first review actually but I will just get right into it without going into too much detail.
First of all, I won't give spoilers. But absolutely this manga is set up in such a way that you have to watch all of the Kakumeiki Valvrave anime for pretty much any of it to make sense or flow well. I picked up this manga because I was interested in Saki Rukino from the anime and was surprised to find a manga featuring her.
The story didn't flow well unless you watched the anime. I thought the manga did provide some important information about Saki that
the anime left out. Due to this fact I rated the manga an 8 overall instead of a 7 after I thought about it a bit.
The manga is worth the time for anyone who liked Saki Rukino's character from Valvrave, because it isn't very long and it does provide some new information about events that happened with her, but most of it can be found in the anime.