4 : Mermaid: The Girl Of Water City -

: Marie provides Bell with critical information about the Dungeon's layout and the monster's habits, establishing a bond that is vital for the party's survival in the subsequent battles. Key Themes and Development

: The episode serves as a precursor to the "Labyrinth Arc" climax, showcasing Bell's increasing maturity and his ability to trust and collaborate with non-human allies even in life-threatening situations. 4 : Mermaid: The Girl of Water City

: The "Water City" setting introduces a shift in tone, utilizing the claustrophobic and unpredictable nature of the underwater environment to heighten the stakes. : Marie provides Bell with critical information about

The episode follows and his party as they navigate the treacherous 25th floor, known as the "Water Capital" or "Water City". While separated from his group during a chaotic battle against a powerful moss monster, Bell encounters Marie , a Xenos (intelligent monster) mermaid. The episode follows and his party as they

Watch the official trailer for the fourth season of the series here:

: The introduction of Marie reinforces the series' ongoing theme of the "Xenos"—monsters with human-like souls—and the moral complexity of Bell’s vow to protect them.