Who Is Mosa-kou? The Case for Shirahoshi
The model for Loki is Loki, the trickster god from Norse mythology. His name comes from Old Norse and means “one who closes” or “one who ends.”
In Norse mythology, Loki tricked Odin‘s son into death. As punishment, he was bound to a cave with a serpent dripping venom on him for eternity.
Out of resentment, he led an army from the underworld to challenge the gods — a truly wild character.
During this ordeal, the woman catching the venom in a bowl to protect him is his wife, Sigyn.
So: Mosa-kou stayed as Loki’s companion for the entire 6 years he was bound to the Treasure Tree Adam. She maps perfectly onto Sigyn.
This means Mosa-kou is very likely the person destined to become Loki’s wife.
…However, Loki already has an arranged fiancée chosen by their parents — and that fiancée is Shirahoshi.
Neptune’s “Fluffy” Daughter
“Here’s to the future of my little rascal and your fluffy daughter!!” / “She is NOT fluffy!!”
Connecting the dots:
→ Neptune’s child would naturally be “fluffy” like him
→ Neptune’s daughter is Shirahoshi
→ Harald tells Loki that his fiancée on Fish-Man Island is “the fluffy one” and gives him her Den Den Mushi number
→ Harald dies; Loki sets out to sea
→ Loki is captured by Shanks and bound to the Adam Tree for 6 years
→ Meanwhile, Shirahoshi has been confined in Hard-Shell Tower for 10 years because of Vander Decken
→ Both lonely, both craving conversation
→ They talked for 6 years while Loki was Shanks’ prisoner
Conclusion: Mosa-kou is Shirahoshi.
The Prince of Elbaf — a nation sitting atop the Treasure Tree Adam —
and the Princess of Ryugu Kingdom — lit by the Sunlight Tree Eve.
Adam is Loki, Eve is Shirahoshi — the first couple in human history from the Bible.
Two people who grew close through years of Den Den Mushi calls — without ever seeing each other’s faces.
Perhaps Imu and Joy Boy were once in a similar situation.
Saint Charlos and His “Never Give Up” Obsession
If Mosa-kou is indeed Shirahoshi, the “traumatic past” she mentioned to Loki is almost certainly this scene at Mary Geoise ↑
And Saint Charlos’s line in that moment reads like pure foreshadowing.
“I did it, Father! With my never-give-up spirit!! I caught a giant mermaid!!” / “Well done, Charlos!!”
Looking back, Saint Charlos has craved a mermaid slave since his very first appearance.
At Sabaody Archipelago, the mermaid Camie was auctioned and Charlos almost won — until Luffy intervened. Two years later, another opportunity came, but he was beaten near death by two of Luffy’s allies.
Saint Charlos is essentially defined by relentlessly chasing mermaids and always failing.
The fact that his father proudly calls it “well done” when Charlos captured a royal in public shows this family has no self-awareness — and Loki’s “never give up” line is absolutely foreshadowing.
This oblivious pair will come after Shirahoshi again.
That means Saint Charlos’s arc is likely to mirror Saint Mjosgard’s redemption.
In the past, Mjosgard enslaved fish-men. When Jinbe became a Warlord, his former slaves (Sun Pirates members) were freed — so Mjosgard sailed to Fish-Man Island to reclaim them.
Shirahoshi Awakens as Poseidon
While Elbaf was under attack by the God’s Knights, Mosa-kou told Loki she wouldn’t be able to call for a while.
Piecing it all together: the Rosward family invaded Fish-Man Island to capture Mosa-kou (Shirahoshi).
Saint Charlos was left in a horrific state by Sai and Leo — but One Piece is half a comedy, so he’s probably still alive.
Having one of Luffy’s allies actually kill someone would create a strange tone for the series.
Even so, surviving in that condition means he’ll likely return looking completely different — perhaps literally half the size he used to be.
If this theory holds, the ultimate destination is Shirahoshi fully mastering her power as Poseidon.
And along the way, we may finally learn the truth about the relationship between the original Vander Decken and Joy Boy.
