Ore dake Haireru Kakushi Dungeon: Kossori Kitaete Sekai Saikyou

Story:

Kossori Kitaete Sekai Saikyou: A hidden dungeon that no one could ever enter… A legendary place full of hidden things, such as extremely rare magic animals, magic tools to win power and other magical things. However, suddenly the entrance was found… "I won't tell anyone about this place, I will secretly become the strongest."