The first thing Ichigo noticed about soul society, even on the streets of the rukongai, was that no one ever touched each other. Not ever.
In the entirety of his experience trying to save Rukia he hadn't so much as seen someone pat someone else on the back. The only contact anyone ever initiated was violent.
Aizen infuriated him. The smug smile and the satisfied gaze of a cat who had thoroughly outwitted the canary and gotten the cream drove him up the wall.
The soul society was in terrible shape, accusations flying, people flooding the fourth for healing- it was a mess. The first thing he did in the wake of the chaos was give Rukia a hug- after being thoroughly berated for putting himself in danger in the first place.
He took careful notice of the way she hesitated before returning the embrace.
As they recovered he put in an effort to extend contact to people. Even ones he'd only just met, or had fought nearly to the death. He shook Byakuya's hand to the shock of Renji and the mild confusion glimmering in the captain's grey eyes.
He clapped Ganju on the shoulder with a grin, engaging him in conversation whever the Shiba looked to be close to starting a fight with any of the shinigami.
The results were slow but irrevocably present. He began to notice people opening up to him easier, like flowers blooming in the sunlight- Renji stopped being so insulting with his remarks on Ichigo's fighting prowess when the orange-haired boy started pulling him in for one-armed hugs and shared cameraderie. Any introduction was punctuated by a handshake or a clasp of arms and a respectful nod- Ichigo couldn't remember the last time he was actively polite and respectful.
Ichigo resolved to keep doing this, keep offering affection and friendship, olive branches by the dozen- Yachiru quickly proclaimed that 'Ichi gives the best hugs!' to the amusement of most.
He hadn't really expected it to come back in such full force so much time later.
He wanted to cry when Rukia stuck the sword through his back, her eyes warm and caring like they'd always been, the line of peope standing in the air, Renji's wild grin, the emotion almost tangible.
Humans die without human contact, souls wither and become cold.
Even Byakuya gave him a small smile as the power flooded through him and once again he felt whole.