Hasumi, a bold young oceanographer, leads a covert expedition aboard the research submersible Mermaiden to investigate mysterious bioluminescent signals deep beneath the Pacific. What begins as a scientific mission becomes a fight to protect an ancient, matriarchal society of sentient deep-sea sisters—creatures whose existence could upend humanity’s understanding of intelligence and kinship beneath the waves.
The best stories don’t have clear heroes and villains. Mission Mermaiden understands this.
When Hasumi faces the Deep Sea Sist, it’s not just a battle—it’s a debate. The Sist whispers truths Hasumi refuses to hear:
Their encounters are gorgeous, chaotic ballets of high-pressure combat and emotional breakdowns. Hasumi’s precision vs. the Sist’s overwhelming unity. Each fight leaves her shaken, questioning her mission, and—slowly—opening up to the very allies she pushed away.
If you’re tired of flat antagonists and stoic heroines who never crack, Mission Mermaiden delivers. The Hasumi vs. Deep Sea Sist arc is a masterclass in:
At first glance, the premise seems deceptively simple. You play as Hasumi, a skilled operative of the Mission Mermaiden corps—an elite task force dedicated to protecting the ocean’s equilibrium. However, the ocean isn't what it used to be. The "Abyssal Rot," a corrupting industrial byproduct, has awakened ancient, mutated leviathans and poisoned the once-thriving coral citadels. mission mermaiden hasumi and the deep sea sist
Hasumi isn’t diving in alone. This brings us to the "Deep Sea Sist."
The "Sist" (short for Sister, a term of endearment for the bio-mechanical companion species in the game’s lore) is named Lir. Lir is a Deep Sea Sist—a being capable of withstanding the extreme pressures of the hadal zones where Hasumi’s organic body would fail.
The narrative brilliance here lies in the symbiosis. Hasumi provides the tactical intellect and the agility; Lir provides the brute strength, the sonar navigation, and the shielding. The story is essentially a road trip through the darkest parts of the ocean, and the writing shines in the quiet moments between firefights, as these two unlikely partners learn to trust one another.
Act I – The Fracture
Act II – The Abyss Trial
Act III – The New Oath
Mission Mermaiden ~Hasumi and the Deep Sea Sisters~ " is an indie 2D side-scrolling action-platformer set in a post-apocalyptic future. The game follows the story of Hasumi, a operative sent on a secret mission in the year 2101 AD to investigate rumors of a biological weapon and strange life forms within the Karimantan Jungle. Key Features
Tactical Side-Scrolling Combat: Players control Hasumi as she navigates an alien-ravaged world, blending traditional platforming with survival-based combat against a variety of enemies and six distinct bosses.
The Deep Sea Sisters: The primary antagonists are a group of adversaries who utilize psychological and physical manipulation—including hypnosis, experimental substances, and technical devices—to thwart Hasumi's progress.
Resource & Status Management: Recent versions and mods, such as The Downfall of Hasumi on itch.io, have replaced traditional health systems with complex resource meters like Willpower, Pleasure, and Corruption, making survival a constant balancing act. Hasumi, a bold young oceanographer, leads a covert
Post-Apocalyptic Survival: The narrative emphasizes a struggle for survival in a high-risk environment where player decisions carry significant weight, leading to multiple outcomes and "bad endings". Mission Mermaiden - The Downfall of Hasumi by NoGag
Mission Mermaiden: Hasumi and the Deep Sea Sist is not a perfect game. The inventory system can be clunky to navigate while bobbing in the water, and some of the late-game backtracking feels like artificial padding.
However, these are minor grievances in what is otherwise a monumental achievement in atmospheric storytelling and unique gameplay design. It dares to be different. It takes the player out of their comfort zone and forces them to adapt to a new set of physics and rules.
For those looking for an experience that combines the tension of a survival horror game with the traversal joy of a platformer and the heart of a buddy-cop drama, this is a must-play. It is a haunting, beautiful ode to the parts of our world we have yet to fully explore.
Final Score: 9/10