@XShakira A severe hit to the head - from a fall or automobile accident, for example - can injure the brain and cause both short- and long-term memory loss. As stated in the manhwa the black haired guy has short term memory loss. Having short-term memory problems means that you forget things you’ve heard, seen, or done. Amnesia is a general term for memory loss. Amnesia isn't the same as dementia. Dementia often includes memory loss but also involves other problems with thinking that lead to a decline in daily functioning. These problems include having trouble with language, judgment and visual-spatial skills. The loss of immediate memory is also termed as fixation amnesia. The clinical features of STM (short term memory loss) impairment, however, are variable and depend on the underlying cause for the memory alteration. The right term I would use is 'short term memory loss or STM' and another right term which you can also use is 'fixation amnesia'.