Many friendships and rivalries help enrich and drive the plot of Bleach, from Ichigo and Rukia becoming friendly allies to Ichigo's feud with Byakuya Kuchiki during the Soul Society arc. Along the way, the lore finds time for many other relationships as well, which can easily deepen and humanize these characters. Even the stone-cold Captain Soi Fon of squad 2 gets this treatment.
Captain Soi Fon is a no-nonsense assassin, a ninja in a world of brash and honorable swordsmen and kido users, but even she has a vulnerable side. Soi Fon succeeded Yoruichi Shihoin as squad 2's commander, and that succession was anything but easy. In fact, Soi Fon and Yoruichi came to blows later in the Soul Society arc, only for their relationship to heal later on.
Yoruichi Vs. Soi Fon: When Master & Student Were Torn Apart
Over a century before Ichigo Kurosaki existed, a daughter was born to the noble Fon family: Soi Fon. She was destined to become a Soul Reaper, and in particular, she was trained as an assassin and stealth expert, a route that not all Soul Reapers take. In her girlhood, Soi Fon met and trained with the legendary Captain Yoruichi Shihoin, and at once, the young Soi Fon took a liking to her. Yoruichi meant everything to her student, from her elegance and beauty to her incredible skills and noble status (the Shihoin family ranked over the Fon family). During this time, Soi Fon would do anything for her beloved teacher.
During the Turn Back the Pendulum arc, the trainee Soi Fon contrasted with the easygoing and goofy Captain Shihoin, and Soi Fon wondered if Captain Kisuke Urahara should really be running around with so little oversight during his experiments. Yoruichi dismissed Soi Fon's concerns, but Soi Fon was vindicated when the rogue Sosuke Aizen stole Kisuke's Hogyoku experiment and created the eight Visoreds one night. This was the beginning of the end for Soi Fon's and Yoruichi's good times together.
Yoruichi loved her student, but she also valued justice and her friends, including Kisuke. Once Central 46 tried to punish Kisuke for Aizen's wrongdoings, Yoruichi broke in and rescued her friend, going into exile to Karakura Town with him at the cost of her entire rank and powerful position in the Soul Society. In Yoruichi's eyes, this was worth it, but she must have felt terrible about leaving Soi Fon behind. Sure enough, Soi Fon was devastated when Captain Shihoin vanished without a trace, and this shock soon gave way to bitter resentment. How could Yoruichi just leave like that?
When Yoruichi & Soi Fon Met Again In The Soul Society Arc
During the Soul Society arc, Yoruichi returned home at last, but this was no triumphant homecoming. Officially, she was a ryoka, a rogue party, and fair game for the Captains and Lieutenants who rallied to defend the Soul Society. Yoruichi was now little more than a criminal invader, and that gave Soi Fon two reasons to oppose her. Soi Fon is a consummate professional, like most Captains, and she wouldn't make an exception for her former mentor. What is more, Soi Fon spent an entire century bitterly resenting Yoruichi for abandoning her without a single word of good-bye. As a Captain, Soi Fon thought she didn't even need Yoruichi anymore. So, when she and Yoruichi crossed paths during the Soul Society arc, Soi Fon had murder on her mind.
Soi Fon showed off her deadly stinger-shaped shikai during the fight and even demonstrated her talent for shunko, a technique Yoruichi herself invented. But in the end, Soi Fon simply could not bring herself to kill her old mentor, even if she had the physical strength to. More than anything, Soi Fon was hurting on the inside, and her sorrow outweighed her anger in the end. Once she and Yoruichi broke even in the fight and Soi Fon exhausted her anger in the fight, she called off the duel and broke down in tears. Yoruichi comforted her as though nothing had happened. Yoruichi always loved her student, and it didn't matter if Soi Fon tried to use lethal force to vent her anger and grief in that battle.
By the story arc's end, Soi Fon and Yoruichi properly made up, at last; fighting side by side in the effort to capture Captains Aizen, Ichimaru and Tosen (who all escaped to Hueco Mundo). Soi Fon had her idol back, and she finally learned to laugh and smile once again, all while resuming her charming idolization of the great Yoruichi Shihoin. All manner of bonus comics and filler episodes depict Soi Fon chasing Yoruichi around, taking pictures and sighing in admiration as Yoruichi simply goes about her daily life. It's all fun and games, but it does prove that even the cold, stern Soi Fon has her warm side, and the very thought of lady Yoruichi fills her with joy. This is a friendship that will stand the test of time.