S-Level Weirdo Trying to Be My Little Brother

In the year 3026 of the Blue Star Calendar, unknown creatures swept across the world. They were indescribable and could not be seen directly. Life and death were unknown in the fog. There is a lord in each fog. Defeat him to upgrade your abilities. Blue Star People's Rules: 1. Don't get close to the fog unless you don't want your life. 2. The weird ones are cunning and treacherous, don't believe them 3. If you accidentally come into contact with the fog, please find a safe area and wait for rescue. The protagonist accidentally gets involved in the fog with an S-level danger level, and fights monsters along the way to level up. Later, he discovers that most of these powerful and strange S-level monsters are the little brothers he beat in his dreams. (I didn't think about the protagonist's name, so I called him the protagonist. The copy may be revised, but the general plot will not change) Intention: Work hard to become stronger!