After recent events, former salaryman Mizuki Ryosuke finds himself the man of the hour! He starts an adventuring business and enters a partnership with the UK government, with Carol's help. Their condition? That he retrieves a broken skill left inside the Omori Dungeon known as "Excalibur." Mizuki's party determines its location, but they aren't the only people on the hunt and a certain familiar face comes to stand in their way. Unluckily for Mizuki, however, there are more threats on this expedition...