Background and Overview
Hinamori is the ex-vice captain of the 5th division under the traitor captain Aizen Sosuke. She is the childhood friend of Captain Toshiro Hitsugaya whom she still thinks of as a little brother. She is a trusting and naive person who forms relationships with others very easily, which is her biggest weakness. She tends to grow very obsessive over people that she forms bonds with and is very hard to change, which is evidenced by how she cannot stop calling Hitsuhaya by his pet-name, even though he is a ranking Captain in a military-esque organization and has to maintain authority over his men. She fell deeply in love with Aizen due to his charisma and deceptive ways and was manipulated by him into nearly killing her childhood friend Toshiro Hitsugaya.
She appears as a fairly normal girl, and does not stand out in many ways. She seems to represent the average person in the comic, and has the most failings.
Despite Captain Aizens betrayal of her, she still finds herself swayed by him into trying to follow him due to her obsessive compulsive tendencies. This makes her a danger to those around her, as she had already shown herself capable and willing to betray her companions for his sake. When she was given a communication link to Toshiro Hitsugaya during a mission he was leading she openly appealed to him to try and save captain Aizen, despite him being the mastermind behind the betrayal of soul society, having nearly killed her and everyone she loves.
Hinamori doesn't appear in the series again until much later. She makes a brief appearance in the Arrancar Arc where she speaks to Toshiro via a monitor. She tells him that Aizen is not bad and that Gin is manipulating him; she refuses to accept her Captains treachery. This shows how mentally unstable she has become. One can even see how ill she is at this point via her appearance. Her speech is interrupted as she is knocked unconscious by the Captain Commander.
Later during Fake Kakura Town Arc, she appears out of nowhere and saves Matsumoto's life from Harribel's three Fraccion. She announces that she now acknowledges Aizen as a enemy and threat to Soul Society, showing that she is slowly getting better. She then reveals that she had hidden her presence using her Kidō and had created a Kidō net around the three Fraccion and Matsumoto. She then uses her Zanpakuto, releasing her Shikai. She uses her blade to cause the Kidō net to explode, "destroying" the three Fraccoin.
Hinamori possesses the standard array of Shinigami powers, though at an advanced level as she is a vice captain. These include Kido Magic (Demon Magic), Air walking, short range teleport (Shunpo) and sword skills using her zanpaktou (Spirit slaying sword). In practice, she is a Kido type who prefers long range magic attacks.
Her sword is named Tobiume (flying plum tree). It is a Kidou type blade that's Shikai release activation phrase is 'snap'. When it is activated the blade straightens and produces several jutted-like prongs along its blade. In this state it is able to fire energy attacks, or release its full payload in a single devastating energy ball. She has proven herself quite skilled with this blade, but its powers are limited by her potential.