Eh to be more clear with this it's actually braine who had his attack mistranslated in the earlier translations of the novels as attacking at the speed of light with his martial arts. Shalltear caught said blade which is where I assume the idea shalltear is somehow related to it comes from. The statement is even more patently ridiculous with context, even ignoring the blatant mistranslation brain is a level thirty character, he at best might be able to parry some bullets based on the death warrior. The idea someone of his level could do anything at "Light speed" is ludicrous. (Anyone in overlord moving at that speed in overlord would be ridiculous within the context of the novels but braine in particular is probably the worst possible character to make such a claim with)
