Rewinding to the week before Ieyasu and Tsunade's prairie moment.
Sumiha, Ieyasu's little sister, was going on her 10th mission as a Chunin today.
It was her first A-rank mission, she was one of two Chunin in a four man squad that was led by an Aburame Jonin and also had a Tokubetsu Jonin sensor.
Their mission was hunting down a Jonin spy from Sunagakure that stole a Fuinjutsu scroll they planned to use for the One-Tails escaped pursuit all the way until the Land of Iron.
Their mission was to join the original search party and look around the target's last known location, not letting him circle around to Suna with the scrool.
This mission was relatively safe as the target couldn't possibly find significant reinforcements so far from his village—plus, with three Jonin-led squads, they had nothing to fear.
The problem was that this mission was going to be exhausting and definitely take a lot of time to be completed.
In the end, the three squads spent a whole month losing the spy's track around one of Land of Iron's coldest prefectures, only to later find the target dead, killed by a group of Samurai for theft.
Mission failed, successfully?
It was a depressing and exhausting month for Sumiha, so when she got back to the village, she was already imagining the hot shower water and her warm bed.
Unfortunately, as soon as she got home, her mother Rumiko looked at her excitedly and said, "Welcome home, Sumi-chan, did you hear the good news?"
Sumiha had headed straight home, so she asked, "What good news? Is it something in the village?"
Rumiko gave a wry smile and said, "No, no, it's your brother, last week he gave us great news."
Even Tokugawa Hirozaku, their father, also nodded, "That's right, the boy finally did something good."
Sumiha was running low on patience, "What about Yasu-nii? Just say it already!"
Rumiko lightly chuckled before saying, "Why don't you go ask him yourself?"
"Ugh, are you two just messing with me? Just say something or say nothing. I'm going to take a bath, I don't care about this so-called good news."
Rumiko finally relented, "Okay, sorry, I just wanted you to talk to your brother first. It's because he's finally engaged!"
"Finally? Isn't it a bit fast? Actually, I take that back, you're right, mom." Sumiha suddenly thought of her stupid brother trying to sound romantic, she couldn't help but shudder. "I don't know what Tsuna-nee sees in him, but it was obvious it was gonna happen at some point. Speaking of which, she might not be around to teach me as much anymore!"
Rumiko could only think inwardly to herself, 'Oh, sweet child, Tsunade will probably want to spend even more time with her sister-in-law now.'
...
Later that day.
Sumiha had already showered and taken a nap.
She went out to the training ground to talk to her stupid big brother.
But when she got there, she didn't see him coolly swinging his blade with sweat dripping down his head like she expected—she saw him completely battered, half-dead with broken arms, sitting against a tree with Tsunade healing him.
"I told you it was a bad idea to block my fully charged kick with your bare hands, this is your all your fault." Tsunade was complaining at his stupid method of testing his strength—even though she beat him up relatively often, she never actually incapacitated him like now.
The flesh and bone of his forearms was completely visible, they were hanging loosely in what could no longer be called an arm, his ribcage broke and his right shoulder was also sunken—a full power kick meant exactly that, the maximum amount of chakra Tsunade could infuse.
Even though it wouldn't take too long for him to heal, Tsunade still hated this disregard for injury—definitely not a hypocrite, by the way.
So, when Sumiha approached, she was shocked by the sight, "Didn't you two get engaged? Did you reject him, Tsuna-nee?"
Ieyasu was kind of dozing off under Tsunade's warm healing, but his body suddenly twitched when he heard that, making him cough blood as he winced in pain. "Hey, brat! Don't slander your big brother. I'll have you know many girls in the Academy-- Urgh!"
Tsunade suddenly twisted his arm, "How dare you start talking about those shameless things? Didn't you say you only cared about me?" She wasn't seriously jealous, but she had to warn him a bit.
"I get it, I get it, please let me heal, though, or we're gonna be here all day." Ieyasu understood. "Anyways, why are you here, Sumiha? Did mom tell you we got engaged?"
"Mhm, I wanted to warn Tsuna-nee about how you might not be right in the head, because I don't think she knows that you keep talking to your naginata like it can actually hear you."
"What? That one time wasn't a joke? How didn't I know about this?" Tsunade had no idea he talked to his blade, she was very surprised there was still such a thing she didn't know about Ieyasu.
"Well, I just didn't want you to think I was crazy. And yeah, I talk to it, but it's really alive, okay? Look here, you can grab it and it won't let you flow chakra through it." After saying that, Ieyasu tossed the Hizakura to Tsunade.
After grabbing it, she immediately used chakra flow as if the blade had been hers for years, "..."
Sumiha, "..."
Ieyasu, "..."
"Yacchan, are you... actually fine?" Tsunade began to ever so slightly doubt her choices at this moment, she needed some answers to feel reassured.
"Hey, don't look at me like that. Hizakura, please don't embarass me, can't you block her chakra?" Ieyasu pleade to the blade as if it was a human.
"Bzz." The blade actually started cutting off Tsunade's chakra, both girls widened their eyes at the seemingly sentient weapon.
"Hey, Yasu-nii, is this thing actually alive? Where did you even find it? And how did you even know it was special?" Sumiha couldn't believe her brother's weapon had really been alive all along—why were the craziest things getting revealed today?
"I've already told you I found it inside a tree in the outskirts of the village before I joined the Academy. I could always feel a special connection to it, then one day it felt alive. That's it, nothing much."
'That's it? Nothing much? Then why don't you give it to me?' Sumiha really wanted to complain, but the way he put it really made it seems like nothing much happened.
"Yacchan, can you hear this blade speak?" As a medical ninja, Tsunade was very curious about the concept of a living weapon.
"Not yet, it can only communicate roughly for now. But I can still feel it growing stronger with my chakra."
"With your chakra, huh? Then isn't it almost like a clone of yours?" Sumiha asked.
"A clone? No way! It's definitely it's own thing, stop daydreaming. By the way, you need to take things more seriously, Sumiha, especially in missions, you should be more prepared." Ieyasu just wanted to change the subject at this point, but this was also something he had been meaning to say.
"Why are you suddenly lecturing me?"
"Did you understand me or not?" Ieyasu glared at her.
"Understood, I'll be more careful and prepare better, now leave me be, I'm going back now."
"Fine, just stay for a few days before going on another mission, you don't need to work so much just because you're a Chunin, it's dangerous." Ieyasu warned again, he really didn't want his family to die, especially not in a stupid or preventable way.
Sumiha just nodded as she walked away.
Then Tsunade layed on his chest and asked, "Is your Hizakura female?"
"Yeah, it- Wait! Urgh!" Before he could justify keeping it a secret, Tsunade and already punched him in the gut and kissed him.
"Shut up, just don't keep any more secrets from me, okay? We're gonna be together through everything now." Tsunade looked at him meaningfully.
"Alright, then I have a confession to make."
"What is it?" Tsunade wasn't sure if he was serious.
"I'm actually the reincarnation of an alien sent here by a divine being." Ieyasu actually said it.
And as expected, he got absolutely battered for spewing "nonsense", but he had said enough to not blame himself for lying—the full truth wasn't necessary anyway.