The final member of the Straw Hat Pirates has yet to be officially revealed, but Eiichiro Oda actually set this up in the story a long time ago. Many fans believe Oda quietly hinted at the last companion to join Luffy about eight years ago, and that character has appeared right before their eyes without them realizing it.
Loki Could Be the Last Straw Hat Pirate

Long before the Elbaf arc officially began, fans speculated that Loki would play a key role. Many even believed Loki would become the final member of the Straw Hats. Seeing him appear in Elbaf and hearing rumors about him joining the crew has sparked huge excitement among the fan community.
Loki was first mentioned about eight years ago during the Whole Cake Island arc, when Big Mom referred to Lola’s failed marriage with the Elbaf prince. This detail quickly made fans realize Loki is an important character with the potential to be the last Straw Hat.
When Loki appeared in the Elbaf arc, despite his seemingly opposing image, he was portrayed as kind-hearted. He expressed a desire to become the Sun God Nika and a wish to set sail and explore. Notably, Loki’s refusal to submit to the World Government perfectly aligns with the Straw Hats’ ideals.

Most importantly, Loki was personally invited to join the crew by Luffy. Fans know Luffy is serious when he extends such an offer, and it makes sense since Luffy believes he’s strong enough to protect him.
Elbaf Doesn’t Want Loki

One of the biggest reasons Loki might join the Straw Hats is because Elbaf doesn’t want him. Loki was rejected from birth. His reputation was tarnished from childhood, and he was never loved in his homeland. Loki is not the monster Elbaf portrays him to be, which is a major reason he may never stay there. They don’t want him, and they never cared about him. Naturally, Loki doesn’t care about them either.
Luffy and Loki Are Destined to Fight Together

If all of this isn’t convincing enough, fans should consider that Loki and Luffy are destined to fight side by side. The Elbaf mural clearly shows the Ancient Giant Loki battling alongside Nika in a great war. This means when history repeats itself, Loki should be by Luffy’s side to fight together.
All the evidence points to Loki being the final member the Straw Hats have been searching for.