Hasumi is dispatched alone. No support fleet. No radio contact. The water is eerily clear. Objective: “Descend to 3,000 meters.” Nothing attacks you for the first ten minutes. This silence is the game’s cruelest trick.
If you choose Option B, the final cutscene shows Hasumi surfacing alone. She writes on her notepad: “They are quiet now.” She salutes the sunrise. No music plays. Credits roll over the sound of gentle waves.
Mission Mermaiden: Hasumi and the Deep Sea Sist is a side-scrolling action role-playing game (RPG) developed by the Japanese indie circle Shitoucchi. Known for its unique blend of fast-paced combat, exploration, and distinctive character design, the game has garnered attention within the indie and doujin soft communities for its polished mechanics and atmospheric world-building.
Mission Mermaiden: Hasumi and the Deep Sea Sist stands out in the indie gaming landscape as a solid action platformer with a strong protagonist and memorable boss design. By combining the exploration of a Metroidvania with a distinct oceanic theme and challenging combat, it offers a compelling experience for fans of retro-style action games.
Mission Mermaiden: Hasumi and the Deep Sea Sisters is an indie platformer set in the year 2101 that follows the high-stakes mission of its protagonist, Hasumi. Tasked with investigating mysterious life forms, Hasumi must navigate a treacherous underwater facility and confront the "Deep Sea Sisters," a group of antagonists determined to thwart her through psychological and physical manipulation. Gameplay Mechanics and Combat
The game blends traditional platforming with a distinct combat system focused on status effects.
Platforming: Modernized camera and movement mechanics allow for precision navigating through the game's submarine-like structures.
Status Management: Enemies use hypnosis, experimental substances, and technical devices to manipulate Hasumi’s mind and body. Players must manage these "statuses," which carry noticeable gameplay consequences and penalties. mission mermaiden hasumi and the deep sea sist
Simplified Battle System: Recent updates, such as those found on itch.io, have streamlined the battle system to encourage more fluid and exciting combat encounters. Key Characters and Setting
Hasumi: The heroine sent on a secret investigation. In various mods and versions, her primary struggle is resisting the temptations and corruption plots orchestrated by her adversaries.
Deep Sea Sisters: The primary antagonists who employ cunning tactics and technical gadgets to defeat Hasumi.
Setting: The game takes place in a futuristically designed oceanic environment, often featuring tight corridors and machinery typical of a deep-sea base. Development and Availability
Originally created by hakkaku, the game has gained a following in the indie and doujin scenes.
Modifications: Popular mods like "Mission Mermaiden: The Downfall of Hasumi" by NoGag improve upon the original by adding more visible content and challenging interactions.
Platforms: Information and ratings for the game are hosted on platforms like RAWG, where it is categorized as a platformer. Hasumi is dispatched alone
Community: Gameplay clips and walkthroughs, such as those on YouTube, highlight the game's pixel art style and experimental mechanics. AI responses may include mistakes. Learn more
Mission Mermaiden: Hasumi and the Deep Sea Sisters is an adult-themed 2D action-platformer game. Originally released around July 2020, it follows the protagonist, Hasumi, on a futuristic mission. 🌊 Game Overview Release Date: July 27, 2020. Genre: 2D Action, Platformer, Eroge (Adult). Setting: Year 2101 AD in a world ravaged by alien invasion. Platform: PC (available on sites like DLsite). 📜 Plot and Objective
Hasumi is sent to the Karimantan Jungle to investigate rumors of a biological weapon. Her primary mission is to confirm its existence and confront the Deep Sea Sisters. These antagonists use various methods to hinder and corrupt Hasumi, including: Hypnosis and mind manipulation. Experimental substances. Technical devices designed for capture. 🎮 Key Features
Combat System: Focuses on magical girl-style battles against unique sea-themed enemies.
Status Effects: Gameplay includes mechanics where "defeat" or specific enemy interactions lead to adult-oriented "game over" scenes or status changes.
"Downfall" Mod: A popular modification by NoGag exists on itch.io, which modernizes the camera and movement while increasing the difficulty of enemy interactions. 🔍 Community & Legacy
The game has gained a following within the indie adult gaming community for its art style and thematic challenge. It is often cited alongside other "magical girl in peril" platformers. If you'd like, I can help you: Find similar games in the genre. Locate specific gameplay guides or walkthroughs. Explore details about the "Downfall" modification changes. Let me know which of these interests you most! AI responses may include mistakes. Learn more Mission Mermaiden ~Hasumi and the Deep Sea Sisters - RAWG Act II – The Abyss Trial
Act I – The Fracture
Act II – The Abyss Trial
Act III – The New Oath
EXT. SHALLOW REEF - DAY
Hasumi spirals through a coral arch, her tail shedding silver sparkles.
MAREN (AI Seahorse): “Heart rate elevated. Nervous?”
HASUMI: “The Sist don’t welcome visitors.”
A deep hum vibrates through water. Hasumi stops.
MAREN: “That’s not tectonic. That’s a song… wrong key.”
Hasumi grips her conch. The ocean darkens 500 meters below.
In traditional shooters, you have an "up" and a "down." In Hasumi and the Deep Sea Sist, the battlefield is a sphere. Enemies can approach from the sand below, the kelp forests to your left, or the murky depths above. Mastering the "Drift-Dash"—a mechanic where Hasumi uses Lir’s bulk to pivot and change direction instantly—is essential.
It took me a few hours to unlearn my land-based gaming instincts. You have to manage your momentum. Stop moving, and you float, becoming an easy target. Move too erratically, and you burn through your Oxygen reserves (the game’s stamina meter).