Phantom Buster Rumi is a rather bad h-game all around and ends up with lacking everything.
The art and animation are both poor at best, with the animations mostly being 1-2 per 'action' (repeated for minutes on end to get to the next scene), followed by seeing all 3 animations at once for a few seconds. The art doesn't even work with the animation, as often Rumi will have parts of her body decide physics and basic connection to her body are not required. This does not improve in any part of the game.
The story is some normal captured hero garbage run through what I hope is a machine translation, which is the only excuse for said translation being so terrible. The sound and voice is decent, although the sound effects during animations and 'gameplay' only have a few sounds and become annoying very quickly.
The gameplay itself is 2 terrible 'shooter' segments, and spam clicking on a few spots for minutes on end so you can slog your way into the next badly animated scene. This repeats over several times.
All in all this is a extremely short (even with the slog it only took ~15-25 minutes to reach the end) 'game' that I highly recommend not downloading. The only exception is if you want a game where you can focus on graphically torturing and beating a magical girl, in which case this has options for that constantly and might be a solid 2/5 game for that audience.