The Great Tidal Bore

Following his intense encounter with the demon Leonore, Rio focuses on strengthening his movement magic and overall battle readiness, feeling the need to shore up his weaknesses. He attempts to figure out a method for rapid movement on land using water jets, similar to how he used them underwater. However, the initial results are comically slow, which he labels as a "work in progress". Rio decides to shift his focus to research, heading to the library to study advanced alchemy texts and lore concerning the Akuma (demons).

Meanwhile, Lyn, a member of Abel's party, the Crimson Sword, is also at the library trying to find information on the unprecedented magic skills Abel described Rio possessing, such as creating thick ice walls capable of crushing golems. Unable to find any historical spells matching Rio's feats, Lyn suspects Rio must be a scammer or that such magic can only be performed by the strongest wizard on the continent. While at the library, Lyn encounters Sera, the elf girl and sole member of the B-rank party "Wind", who has just returned from a mission.

The dungeon situation, which the instructor insisted was safe, rapidly escalates. Amon, Nils, and Eto return from their dungeon excursion and report finding goblin archers on the fifth floor. These monsters are typically only found below the 10th floor, causing Guildmaster Hugh to realize this signals the potential start of a major crisis: the Great Tidal Bore, which is the ominous explosive rise in monster numbers. Hugh orders Nina to summon all B-rank and above adventuring parties, which in Lune means assembling the Crimson Sword (Abel's party) and the White Brigade. Abel is visibly irritated at the prospect of working alongside Phelps, the leader of the White Brigade.

Rio continues his quest for advanced knowledge, traveling to the Northern Library. There, he reconnects with Sera, who is captivated by his presence. When Sera asks what he is looking for, Rio quickly pivots from researching akuma to claiming he wants to study alchemy to create golems. Sera, impressed by his ambitious goal, agrees to guide him through the library stacks, where they discuss books and adventuring. Sera confirms she is the only elf in the city, an oddball who chooses to live among humans.

At the dungeon entrance, just as the doors are about to be opened for investigation, Abel senses danger and uses his instincts to stop Hugh. Abel instructs Lyn to scan the area with wind magic, and she confirms that hundreds of monsters are lying in ambush just behind the gate, proving the monster outbreak has already begun. Hugh immediately commands everyone to fall back to the walls and alert the knights.

A massive battle ensues on the city walls against a horde of goblins that smashed through the dungeon gate. The knights soon arrive to reinforce the adventurers. Nils helps the war effort by bringing arrows to Abel's party and relays Hugh's message: the Crimson Sword is responsible for taking down the boss monster after the initial mobs are cleared.

Once the main goblin force is defeated, Abel and Phelps lead their parties into the dungeon's breach. They encounter three Goblin Generals, which makes Abel realize they are facing a Goblin King. Before they can fully engage, the Goblin King emerges from the dungeon, using a powerful wind slash that instantly kills all three of his own generals. Abel and Phelps attack the king together, but their weapons fail to pierce his thick armor. Abel attempts a direct strike, utilizing his Perfect Shadow, a ghostlike dodging skill and Total Impalement combat technique to pierce the King's chest, but the blow is insufficient to finish the job. Abel calls on Lyn, who unleashes her ultimate wind spell, Bullet Rain, which passes through Abel's ghostlike form and finally destroys the Goblin King.

The adventurers celebrate their hard-won victory. However, the episode concludes by hinting that the nightmare is far from over, revealing that something even more sinister is sealed behind an eerie, untouched black door deep within the dungeon.