Tatsuki Arisawa

Tatsuki Arisawa is one of the main supporting characters in Bleach.

She is Ichigo Kurosaki's childhood friend and one of the few ordinary humans in his inner circle who remains mostly uninvolved in the spiritual/supernatural battles for most of the series.

Key points about her:

• Tall, athletic, short dark hair (usually styled in a practical, slightly messy way)
• Extremely strong-willed, tomboyish personality, and fiercely protective of her friends (especially Orihime Inoue, her best friend)
• Highly skilled in karate — she's the regional champion in her age group and very physically capable
• Brave and straightforward; she's one of the few people who can openly call Ichigo out or even physically intimidate him when needed
• Generally serves as the grounded, no-nonsense "normal" friend who notices when strange things are happening around Ichigo but usually stays on the periphery of the spiritual plot

She's best known for her loyalty, toughness, and the memorable moments where she stands up to much more powerful beings purely through sheer guts and willpower.