Sayaka Nagisa (渚 さやか) is ChangeMermaid of the Changemen.
Former Strategic Branch officer with the Earth Defense Force. A genius with the "brain of a computer," Sayaka is also an inventor. A stickler for manners and etiquette, her "Miss Perfection" attitude frequently clashes with Mai's rough and tomboyish nature. A loving and caring person in a motherly way, Sayaka, like Tsurugi, often becomes more emotionally attached to cases than she should, which is why the two most likely share a good rapport. Loves animals. Frequently comes up with the plans to be rid of or discover the Gozma's attacks, she always gladly works with Tsurugi. Tsurugi always shows constant faith in her, as shown when her invention of the Anti-Grav Belt to combat a flying Space Beast Warrior initially failed, injuring and angering the others on the team, while Tsurugi remained with her to continue its testing. Due to moments like this, the team wonders if Tsurugi and Sayaka are an item, and have tormented them about it.
As ChangeMermaid, she is armed with the Change Sword and Mermaid Zooka, which becomes the scope for the Power Bazooka. Due to its size, the power of the Mermaid Zooka itself is weaker than the rest. Her unique combat attribute is the grace of her movements, while anticipating her opponents next move with her intelligence, often being able to discover her opponent's weak points. Copilots Helichanger 2 with Griffon.
- Shuttlebase (shared with Dragon, Griffon, Pegasus, and Phoenix)
- Helichanger 2 (shared with Griffon)
- Change Brace
- Change Sword
- Auto Changer
- Jet Skis