|“||Do you also wish to enroll? That would increase the number of people wearing glasses around here.||”|
Shiori Usami (宇佐美 栞 Usami Shiori?) is a character in the manga and anime series World Trigger. She is an Operator and a member of Border's Tamakoma Branch, serving as the Operator of Kizaki Unit and Tamakoma Second, being originally a member of Kazama Unit, and also serves as an Operator for Yūichi Jin despite (or due to) the fact he's a solo agent. She is also the creator of the "Yashamaru Series".
Shiori is a young woman with fair skin complexion, dark purple hair and dark brown eyes (both black in the manga). Her hair is styled in a hime cut, a hairstyle common in Japan. She wears correction lenses, in the form of red-framed glasses.
She is usually seen wearing a long-sleeved purple cardigan with black stripes around the edges and a number on the left chest, along with a white dress shirt, a tan skirt, dark purple kneehigh socks, and dark blue loafers. When she was still part of Kazama unit, she was seen wearing a hoodie over a white shirt.
When in Operator duty, she wears the default Border uniform.
Shiori is a very playful and carefree person, as shown throughout her appearances in the manga. She also seems to be a nerd and enjoys analyzing things. She is shown to be very childish, inviting Osamu simply because that'd increase the number of people who wear glasses on Tamakoma Branch, and crying when Jin interrupted her when deciding Chika's position.
Usami likes pampering Chika, and always helps her during Rank Battles.
They are cousins. They seem to have a really good relationship, as Yoneya is seen taking care of Yōtarō on her Usami's behalf.
Usami maintains good relations with her former unit, though she is annoyed by Kikuchihara's blunt nature.
- (To Osamu Mikumo) "Do you also wish to enroll? That would increase the number of people wearing glasses around here." 
- (About Tamakoma Branch) "Except Jin-san, there are only 3 more people composing our self-defense group members. The Tamakoma Branch is a group composed of only a talented select few!" 
- (About Kazama Unit) "Now... When people think of "camouflage", they think of Kazama Unit. A unit with a motto, brilliant!" 
- "Shiori" (栞?) means "bookmark/guide", which fits her intellectual and didactic personality.
- "Usami" (宇佐美?) is a common Japanese surname.
- She likes glasses, reading books and looking after people.
- She has been hinted to be the older sister of Aya Usami from Super Dog Rilienthal, but this is unconfirmed as of yet.
- Her voice actress, Eri Nakao, also voices Ichinose.
- In an episode Omake, Yūma calls her an "explanation freak", after she explains him the differences between Gunners and Shooters.