The Southern Undersea Temple (南の海 Minami no umi) is a location in Monster Girl Quest. They are the seas surrounding the Natalia region of Sentora. These seas are ruled over by the Kraken, guardian of the Blue Orb.
Luka initially travels to this area upon receiving a request from the mermaid Meia, who wishes to marry her lover. To allow him to travel underwater, she gives him the Ball of Guidance. Along the way, he is confronted by a Jellyfish Girl, a Sea Anemone Girl, and finally an Anglerfish Girl. He eventually arrives at the great temple that houses the Southern Seas' ruler. However, when Luka tries to explain his intentions and lets slip that he's a "hero", Kraken immediately assumes that he wants to steal the Blue Orb and attacks. There is an intense battle in which Luka uses his hidden powers (thanks to Alice's intervention). Kraken still refuses to give up the Blue Orb, so Luka explains his intentions. She agrees to the marriage, then slingshots Luka back to the surface as "compensation" for her hasty actions.
In Chapter 2, Luka returns to Kraken, with no interference from other monsters, and asks her for the Blue Orb. She willingly hands it over and wishes him well on his journey.