Via a dream!

Minato, sleeping next to a naked Musubi, and a naked Miya on his other side, was moving fitfully. He was having a rather vivid dream. One that could easily be confused with reality.

He was in a forest, walking around, wondering just where he was. He was reminded of the countryside near where he had used to live. He then paused as he heard something from a little deeper in.

"Waah... *Sniffle,* waah..." the sobs were being heard loud and clear to him, and he turned curiously towards the source.

"Someone... Crying?" he asked aloud, before walking towards it. His sister often cried while they were growing up, usually when she had gotten herself into some kind of trouble. Was that her? Was this a lucid dream of some good old times? He walked towards the sound, before seeing a silhouette up in a tree. Still assuming this was a dream of one of his memories, he played along with the events. "Ah, Yukari, got yourself stuck in a tree again?" he asked as he approached. "Big Bro's here, so no need to cry."

The figure sniffled again, before turning her face towards Minato. He then stiffened. That wasn't Yukari. It was a different young woman. "*Sniffle,*" she sniffed again.

He stared a moment. He realized she was the girl he had seen before in that odd vision. Wait, was this even actually a dream, or something more? Deciding not to question it too much for now, he stepped beneath the branch, and held out his arms. "Come on, you're fine, don't be scared," he told her. "If you come down, I'll be sure to catch you..."

Looking at him with a good deal of shyness, she hesitated... Before after a moment of working up her nerve, she literally kept down from the tree. "Oof!" Minato yelped, not expecting her to come down so suddenly, and as a result, got tackled down to the ground.

It actually reminded him of the first time he had met Musubi. With a groan, he sat up as she got up off of him, and sat beside him. "Thank you..." she told him quietly, looking away.

He gazed at her a moment, trying to glean as much info as he could from her by looking. She seemed rather socially awkward, and slow to trust. She had a short, slender build. Based on her appearance, she was either an older teen, or a young adult, she was in that area where it was kind of hard to tell until she was asked her age.

"Um, what's your name?" Minato asked after a moment of regaining his bearings. "Do you mind telling me?"

She turned her gaze back towards him, and flushed a bit. "...Ku- Kusano," she stammered.

He smiled and slowly patted her head. "That's a cute name. Do you mind if I call you Ku-chan?" he asked her.

She smiled at the action and compliment, and nodded her assent to the nickname almost immediately. His kind air made her feel more comfortable around him. "S-sure," she replied.

"...so... What exactly are you doing out here? What's going on?" he questioned.

(So yeah, Kusano is aged up, so her appearance is a little different. Mostly her being bigger than in canon. Still small, but not so much that she wouldn't be believable as an adult.)