The stage setting of an underground resource development survey project, set against the backdrop of Earth facing an unprecedented energy crisis, is truly outstanding. The sharp worldview depicting contact with subterranean lifeforms captured from the depths of a primeval forest cave in a future where humanity is declining irresistibly draws you in. The greatest charm of this work lies in the depiction of instinctual acts between the subterraneans, devoid of dialogue. The males greedily pursuing the females, conveying passion solely through moans, captures the moment primitive energy erupts—it's a tour de force.

Particularly, the structure where interactions with the male subterraneans occupy the majority of the main story highlights the taboo intermingling with a different species, making it visually stimulating as well. However, honestly, I wished for more sex scenes between the female subterraneans and humans. If there had been developments where researchers toy with them under the guise of ecological surveys or a more intimate human relationship depicted in an 'experimental chapter' approach, it would undoubtedly have added depth to the worldview.

While there are countless fantasy works, an AV that goes this far in its setting is rare. Special expressions like split tongues also enhance the role that only this actress can pull off—excellent casting. I want to applaud the production team's challenge, but the excessive color grading in the scenes between subterraneans leading to overexposure is a pity. I hoped for a more natural depiction of instinctual behavior.

Overall, this is an ambitious work that masterfully blends the realistic theme of energy issues with fantasy elements. The successful balance of eroticism and worldview makes it a piece that expands the possibilities of AV.