Koyori Akutagawa is a reoccurring character in the series W'z and was the the female protagonist in the anime Hand Shakers. She is known as 'Sprocket Gear' and together with Tazuna, they are known as Team Gear. She's also a transfer student from Brazil. It was revealed that Tazuna needed to hold her hand at all times to keep her life span stable but by doing this they can easily be identified as Hand Shakers.
Koyori is a very quiet girl who communicates through her actions. She is very kind and sweet. From the fights you can see that she is also very brave. While 10 years later she is shown to be more healthy and mature and more outgoing.