Multi-Dimensional Bomb (ＭＤ爆弾,Maruchi Daimenshon Bomu), also known as a MD Bomb (ＭＤ爆弾,MD Bakudan), is a device that Kokonoe is implied to have created and be in possession of. In BlazBlue: Chronophantasma, Kokonoe claimed to have implanted the device inside Ragna the Bloodedge's Idea Engine as a means to keep him and Celica A. Mercury close to one another. If the two were to become separated from one another, then the bomb would detonate, killing Ragna and a great many others in the vicinity. Throughout the majority of BlazBlue: Chronophantasma, the threat of the MD Bomb greatly limited both Ragna and Celica, hindering their process and leading them to be constantly in each other's presence.
In reality, the MD Bomb was never implanted on Ragna, instead, a machine to gather data was the true object placed upon him. The MD Bomb was merely a cruel ruse so that the duo may stay together long enough for Kokonoe to analyze the date gathered and create the Noise Canceler for Celica.