With a cracking noise, something within his body let out a cry. The blood vessels on the back of his hand swelled up oddly. He became strongly aware that he had thick blood pipelines running from his fingertips to his shoulders. As soon as he noticed that, something tore. His skin ripped from the inside and a dark-red liquid squirted out.
[...]
The damage did not remain in just one place. The flows of the arteries, veins, and nerves running through his entire body like spider webs gave him a strange pulse and pain while bringing their presence to the front of his mind. He was made strongly aware of the expansion and contraction of his organs as well as their locations. More sweat flowed from his body in an instant than if he were to enter a sauna. That clear and unpleasant liquid mixed with something red. Accelerator thought small scale explosions were occurring in various places across his body. That prediction was not wrong.

A Certain Magical Index Volume 22, pg. 67