No the comic with Vaders secret apprentice is the force unleashed based on the videogame. The one i am talking about features his Jedi apprentice Ahsoka Tano during the clone wars when he trains her in the ways of the force. Based on the Cartoon Network series.
and by Manga i mean japanese comic, too bad it was flopped as a mirror image by Dark Horse Comics. I have spent years trying to find the Media works japan release.
They adapted everything but Attack of the Clones and Revenge of the Sith. in terms of the six star wars films. Phantom Menace by Asamiya was very bizarre however almost like a cartoon rather than an anime or manga.