Mission Mermaiden - Hasumi And The Deep Sea Sis... Link

A unique feature of this event is the Pacification System. You do not have to kill the Sisters. If you bring Hasumi and a "Merchant" class character, you unlock dialogue options that lead to a "Good Ending" where you heal the corruption. This unlocks a secret boss: The Void Leviathan.

Hasumi learns she is a Mermaiden—a human with the soul of a mer-warden. Her mission: locate and awaken the Three Deep Sea Sisters, each guarding a fragment of the Ocean’s Heart: Mission Mermaiden - Hasumi and the Deep Sea Sis...

The "Deep Sea Sisters" are not generic bosses. Each sister represents a different aspect of oceanic peril, requiring unique strategies to pacify. A unique feature of this event is the Pacification System

The pressure at two thousand meters doesn’t just crush — it confesses. Hasumi’s skull sang with the weight of every shipwreck above her. Then the Sisters arrived, not as monsters, but as a question written in light: “Why do you carry your dead sister like a stone in your chest?” The pressure at two thousand meters doesn’t just

The title’s playful "Sis…" hides a tragedy. The fourth, unspoken sister—Umiko—was corrupted by the Black Tide centuries ago. Now a hollow siren, she hunts her own siblings, whispering:

"Why wake them, little mermaid? They left me in the dark."

Umiko isn’t a villain but a broken sister, and Hasumi’s true mission becomes one of healing, not destruction.