Trying to recall a canvas webtoon I read back years ago, where the male mc suffer from brain damage blanking back and forth from reality to a fantasy/another world.

From bits and pieces of the story that I recall. The male mc was on a train where he got into a fight with two thugs or gangsters. That were carrying some kind of suitcase that was to be transported somewhere. Then it was reveal that those gangsters were being set up or were being tailed by a girl and a older guy. Until the mc step in which he then joins their group to fight against a large organization or gang within the city. The girl and mc go out into city together but were caught by the group. They were then chased and corned into a fight where the male mc was hit in the head by a bat. He then saw the wall covering the city break apart as black monsters poured in. He then wakes up in another world only to get into a fight with a creature. He was then found and taken care of by a woman and her brother I believe. After resting in her house, he than awakes back into reality only for a moment before slipping back into that world.