She didn't really have much of a reason to run away from home to begin with, it was just a slight misunderstanding between her and her father born from the loss her mother. The only things that kept her from going home was the search for her mom's star and the Kabutonga movie. And once that was resolved, there was no reason for her not to go home.
“Then I'll help you out”
“Really!?”
Kii's expression lit up once more from Koutarou's unexpected offer. Her mature expression vanished and her childish smile returned.
“Then promise me that you will go home once it's done”
“Okay! I promise!”
Kii accepted Koutarou's proposal with a smile, since it was a welcome one for her as well. No matter how clever she was, she was still only six years old. There was no way she wouldn't be anxious after running away from home all alone. She had no reason to refuse Koutarou's proposal after he had reached his hand out to her and spent a few hours with her.
“Here”
With a smile, Kii looked up at Koutarou and showed him her right hand.
“What?”
“A pinky swear. It's a promise, right?”
The girl formed a fist with her right hand and reached out with her pinky. Seeing that, Koutarou did the same as the girl and they twisted their pinkies.
“Pinky swear♪ If I lie I will swallow a thousand needles♪ Pinky sworn♪”
Thus, after exchanging their promise, they began moving together.