Bleach: The Captain, Toshiro Hitsugaya x OC

Terms of Interest: A Seireitei Index

*Some descriptions are taken straight from the Bleach Wikia, as they offer the most comprehensive definitions/explanations*

[A]

Aizen, Sosuke: Former captain of the fifth division, he betrayed the soul society and fled to Heuco Mundo to plan his attack. He had the entire seireitei convinced he was a quiet intellectual while gaining his followers Ichimaru and Tosen. He uses a zanpakuto that has the ability of perfect hypnosis. 

[B]

Bankai: The second released form of a zanpakuto. All captains must have the ability to perform this ability. The zanpakuto evolves when a bankai is released.

[C]

[D]

Division: Also known as a squad. There are thirteen divisions in the soul society. One captain is assigned to each division.

[E]

Espada: Highest ranked among the hollows, they can hold a more human-like form. Espadas answer directly to Aizen and are enemies of the seireitei.

[F]

Fon, Soi: Captain of the second division that specializes in the stealth force. She holds Yoruichi in high esteem.

[G]

Gigai: A mannequin-like disguise that shinigami use to operate like a human in the world of the living. Developed by Kisuke Urahara.

[H]

Haori: a traditional Japanese kimono-like jacket that is worn over a kosode. The captains of the thirteen court guard squad wear a white haori with the number of their squad indicated on its back.

Hell Butterfly: Also known as Jigokucho. They guide the Shinigami through the Senkaimon when traveling between the soul society and the human world. Jigokucho are also used as messengers among Shinigami, often carrying important orders. Jigokucho, like the Shinigami themselves, are only visible to spiritually aware beings.

Hinamori, Momo: lieutenant of the fifth division. She was gravely injured two months prior after a showdown with Sosuke Aizen. She is still faithful to Aizen and is the close childhood friend of Toshiro Hitsugaya.

Hisagi, Shuhei: Lieutenant of the ninth division. Suhei is the editor-in-chief of the seireitei communications, a magazine published in the soul society. He is friends with Akira Yuki.

Hitsugaya, Toshiro: Captain of the tenth division and the youngest to be given the post. He gets offended easily when he is treated like a child because he is so young. His childhood friend is Momo Hinamoro and he is very protective of her. 

Hueco Mundo: a parallel universe where hollows congregate; the base of operations for Aizen and his cohorts.

[I]

Ichimaru, Gin:

Ise, Nanao: She is a very serious and pragmatic person who often puts up with her captain's silly antics, but like all lieutenants, she is extremely respectful of her captain and follows his instructions without hesitation. She is almost always carrying a heavy book.

[J]

[K]

Komamura, Sajin: Captain of the seventh division. Komamura is an anthropomorphic wolf, although he is often mistaken for a dog. Initially, he was very self-conscious about his appearance, so he wore gloves with bracers, as well as a helmet, to conceal his entire body. However, he later gains enough confidence to go on without his helmet.

Konso: a soul burial ritual performed by a soul reaper by pressing the hilt of their sword (zanpakuto) on the forehead of a lost soul in the human world and transporting them to the afterlife.