In the manga, Senjumaru did not employ Bankai. The character's abilities and actions were depicted differently without resorting to this particular power.
Shinji did use his Bankai in the manga. It was a crucial moment that turned the tide of the fight. The Bankai's power and unique abilities were showcased, adding an exciting element to the story.
One interesting 'harry potter bankai fanfiction' could be where Harry discovers a hidden power within himself that combines the magic of Hogwarts with the concept of bankai from 'Bleach'. For example, he might use it to defeat Voldemort in a more spectacular way than in the original series.
Another way is through character development. A character in Harry Potter, say Neville, could go on a journey to master a bankai - like power. This could involve him training in a special place, like the Room of Requirement, which could transform into a training ground similar to the ones in 'Bleach' for bankai training. He would face challenges and grow as a character, all while blending the two concepts.
There was a novel called " Happy Everyday, Free and Unfettered Immortal " that mentioned reincarnation or transmigration. This novel was a classic Xianxia novel. It told the story of the protagonist, Fang Yun, who was reborn into the world of happiness every day. He used the experience and skills accumulated in his previous life to become a strong person in the world of happiness every day. Not only did the novel have wonderful battle scenes and character creation, but it also had profound philosophical thinking and emotional descriptions that were deeply loved by readers.
Song: Missing You
I miss you every day
Your smile is so cute
every night
I miss you silently
I miss you every moment
Your figure is so charming
in my heart
You'll always be my one and only
I miss you in spring, summer, autumn and winter
Your gentleness is so moving
in every season
I wish you happiness
I miss you every moment
Everything you have is so precious
in my world
You'll always be my baby
I miss you, miss you, miss you
You are my eternal wish.
I miss you, miss you, miss you
You are the most precious gift in my life.