A mysterious signal emanates from the Mariana Trench. Deep-sea creatures known as "Abyssals" or "Sirenids" begin disrupting global shipping lanes. The protagonist’s academy/organization deploys its most analytical operative: , a sniper/specialist known for her cold calculations. Her mission? Descend to the ruined underwater city of Aquatica and locate the "Deep Sea Sisters"—three legendary mermaid-like beings who hold the key to stopping an ancient catastrophe.
: The definitive challenge mode unlocked exclusively after completing the campaign. It heavily penalizes positioning errors and demands mastery over the module configurations.
Focuses on physical strength and protection, often using the strength of sea mammals to fight off threats.
The narrative is propelled by a fully voiced Japanese cast (CV) Moegirl that breathes personality into the dark atmosphere: Mission Mermaiden -Hasumi and the Deep Sea Sist...
Hasumi kept strict ethical rules: no baiting, no loud or prolonged intrusions, and an open research log shared with local communities and regulators. The mission prioritized observation and respect over exploitation.
is an action-platformer and adult eroge game developed by the indie circle Hakkaku (八角家). Released on platforms like DLsite, the game blends fast-paced side-scrolling combat, deep sci-fi lore, and pixel-art visuals with defeat-based scene mechanics. Taking inspiration from games like Echidna Wars DX , it has earned a dedicated following in the adult indie gaming scene. Core Gameplay Mechanics
Within various gaming communities and forums, the game has been noted for its distinct visual direction and the challenge posed by its boss encounters. Enthusiasts often discuss the mechanical nuances of the "Deep Sea Sisters" and share strategies for overcoming the various debuffs encountered throughout the Karimantan Jungle. A mysterious signal emanates from the Mariana Trench
A junior marine biologist at the quiet edge of the Kuroshio Current, Hasumi’s days had been occupied with routine transects, plankton nets, and late-night coding to clean acoustic data. The sea was a notebook she kept in pencil—patient, careful, easily revised. Then she heard something that did not belong to notebooks: a pattern in the abyssal hum that felt like language.
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The game follows Hasumi as she travels to the remote and deep-sea environments to confirm the existence of a rumored bioweapon. Players navigate dangerous underwater structures and submarine-like bases while engaging in combat with specialized enemies. Genre: Action Platformer / 2D Adventure Her mission
The found in the Karimantan Jungle. How the game connects narratively to the prequel title . Share public link
: Navigate side-scrolling levels by jumping between platforms and utilizing a mix of melee and ranged attacks to defeat robotic and biological enemies. Escape Mechanics
: As an adult-oriented title, the game features explicit "game over" animations and defeat scenes. If Hasumi's health pool is depleted by enemies, local fauna, or bosses, unique adult-themed sequences trigger based on the specific enemy that defeated her. Boss Encounters
: Hasumi must face off against a variety of enemies who use psychological and physical tactics to gain the upper hand. These opponents utilize hypnosis, experimental substances, and advanced technical devices to manipulate their targets.