What if... the saniwa is blind? She meets Manba-chan for the first time and she's a lil bit surprised coz a sword can talk, which confused him (she wasn't informed abt the swords having a human form bcs konnosuke forgot to tell her or he left her to find out on her own)

"The sword... is talking?" She says.
"W-why are you so surprised? I'm standing in front of you"
"Swords can stand by themselves?"
"Wh-Master, I have legs, can't you see?"
"Uhm... forgive me, I didn't realize you have legs since I can't see you."
"Can't see?"
"I'm blind."

Manba's eyes widened in shock. How can someone like her fight against the history retrograde army?
"Don't underestimate me Yamanbagiri Kunihiro, I can't fight alongside you in this state but I can support you" she says smiling confidently.

"Now, since you have a pair of legs then that means you have a human body, right? Come here so that I can look at your face."
Look? At his face?? WHEN SHE'S BLIND??? The girl is crazy, Manba thinks. And just when he thought it will be easier on him since she can't see his face

"But how can you see when you are blind?"
She explains to him that she 'sees' through touch. Manba-chan is hesitant at first but still listens to her anyway and crouches down to her level on the floor. He remains silent as her fingers gently and lightly touch parts of his face

At first she uses one hand to identify his nose, eyes and lip, then she uses the other to find his hair bangs and touches his hood.
"Why do you cover your head?"
"It's... to help me hide my face"
"From enemies?"
"Yes"
"Well... you're not facing enemies now aren't you?"
...

She holds his face in between her hands
"Don't hide your beautiful face, Yamanbagiri."
He almost wants to cry, biting the inside of his cheek. Even when she is blind, she still calls him beautiful. It brings him a little bit of joy somewhere in his beating heart

Until he reminds himself that his new master has yet to know about his origins. Will she still see him as beautiful when she finds out?

K I'm done time to cry

More headcanons about blind!saniwa (ง ˙ω˙)ว 
Hasebe is SUPER careful with her whenever it's his turn to be the secretary for the day. He's constantly making sure that the floors of the inside of the citadel is cleared after one incident where she trips over a small ball (p1)

(p2), which also means he's always reminding everyone else not to leave random objects all over the place. It gets annoying sometimes but they all know he means well and learn to be extra careful with their things.

(p3) at one point when few of the awataguchi tantous were running through the corridors of the citadel (which was after they have recently manifested), they accidentally bump into her and Hasebe yelled at them to be careful poor things

The saniwa had to comfort them before the waterworks began, telling them that it's alright to play but either be careful if it's inside or play outside. She also had to tell Hasebe to tone down the yelling when he's scolding the little ones

(p5) he did tone down the yelling... for a month, but by then everyone is already used to it . The saniwa got worried when she heard him screaming one day and had to brisk walk to the dining hall to find out what happened. By the time shw got there-

-she heard hysterical laughter and squealing instead. Even Hasebe's. Imanotsurugi saw her in the doorway and explained to her that Kanesan and Mutsu has started a food fight, which Hasebe then everyone else got involved lmao

ANOTHER HEADCANON
blind!saniwa is rlly good with her hands, her favourite past time is making handmade snacks in the kitchen. Sessions in the kitchen involves exhanging and learning new recipes with Micchan :>

Micchan always asks her for a second opinion when it comes to taste testing a dish. Even when she's not in the kitchen, he would ask her to come for a short moment to take a sniff or have a taste.

Oh yeah, EVERYONE in the citadel loves blind!saniwa's rice balls. The first time Hasebe tried one, he was moved to tears.