This is the second volume of the light novel series. It was a "successful" web novel series that was published afterwards which in this special case has made this story better (cleaned plot holes and made the story better according to the afterwards by the author). This second volume has 5 chapters and bonus content and close to 200+ pages.
The author has made the main character, Arihito Atobe, (Strongest Rearguard) rather addicted to success, so every mission, everything that he gets his team to do, is won by the seat of their pants, winning with impossible odds. There is such a incredible difficulty level in everything they do, so much so, that it makes the story not that credible anymore. It's not that one as a reader wants the main characters to fail, it's that their success streak is going for too long, too hard, and thus not credible.
The main character's arrogance or naivete makes him decide, in this volume 2, to take the trials of the Seventh District (even thought they had already been approved to pass, because of the help their team made during a Monster Stampede). This places their team under an extreme and unneeded danger. If they had already passed the trial, what did they have to gain by taking the trial anyways? Everything is life and death here at the Country's Labyrinth, alternate reality world. I feel this team of seekers is making bets their bodies can't cash, and thus feel a somewhat ominous "destined to fail" premonition.
If at the beginning it seemed that this world was a kind of purgatory, one perceives a constant persistence of evil, to completely annihilate everybody, not just the seekers (reincarnated people looking to improve their levels) but also the seekers that support them (guild, marketeers, smiths, etc.)
Even though members of the team of main characters have weird jobs (professions): Gambler, Shrine Maiden, Valkyrie, Rogue, Swordswoman, and Rear Guard, the additions of the Silver Dog, and others have solidified the missing strengths needed to survive and overcome. More than the total of their individual skills, the coolness under pressure and the unending attitude to overcome by Arihito, is what has kept them alive and at number one of success as a team of seekers. I feel Arihitto lacks humility and a strong fear of failure. Because of the car accident where his parents died, and all of the tragedies that he lived in his former lives, he is risking more and more the lives of his team members (without really gaining anything). Well, they gain experience and levels, but they are risking their lives (of completely wiping out) in everything they do.
The monsters in this volume 2 are more about debuffs, mind and sense control. Because most of the team members are still of the lower levels, they have yet to complete all of their vulnerabilities.
Author mentions that in addition to the web novel, and this light novel (up to Volume 6 so fat) they have plans for a manga version of this World Strongest Rearguard.