I didn't give Rin and Gou specific age, but they are something 7-10 years old. Prior Rin transfered to Itawobi, anyway :D

"Here's some money so you can get ice cream or something", Mom said and handed over some notes to her son. "And remember—"

"To stay on the hotel street", both kids replied at the same time while Rin put the money into his pocket. He opened the hotel room's door and they stepped out.

"And Rin, remember to take care of Gou", mother called after them. "And be back in two hours!"

"Yes, yes!" Rin said. His sister giggled.

They came out of the hotel and decided to go to left, as they remembered there was an ice cream booth nearby. Matsuoka family had come to vacation to Okinawa. Unfortunately their mother had not felt well that day, so she had let her kids go out so they wouldn't be bored in the hotel room. But she had made them to stay on the street where their hotel was, as it was a pedestrian street so there weren't cars, and not to go to beach. Rin was bit annoyed because of this because mom knew very well he could swim, and the beach was just one street away from the hotel. He could smell the ocean. But, since Gou still hadn't learnt to swim that much, he had to spend this day on the dry land.

Gou spotted the booth and pointed it to Rin. There was quite a long line, but because they weren't sure was there another anywhere near, they stayed here. There was a bench middle of the street. Rin lead Gou there.

"I'll go buy them. What do you want?"

"Strawberry", Gou replied and sat on the bench.

"Okay. Wait here. Don't move an inch, got it?" He shook his index finger in front of her nose. " Don't. Move!"

"Okay!" Rin went to stand to the end of the line, thinking which flavor he would get himself. There were about eight people before him.

Gou swung her legs back and forth and looked around the street while waiting. Then she spotted something interesting, which made her forget her promise to her brother completely.

Rin was second in the line. He was still battling between vanilla and apple. He turned to look at Gou before it would be his turn… and saw she wasn't where he left her!

He felt his heart jump into his throat. Rin rushed back to the bench and looked around, but couldn't see his sister anywhere.

"Aah!" He cried out loud and grabbed sides of his head with his hands. I told her to WAIT! If mom finds out I lost Gou, she's going to kill me! He made turned around in full circle to check she really wasn't anywhere near. I'll have to find her before we have to be back. She couldn't have gotten far! But which way did she go?!

Two benches away sat an old man that Rin had noticed already before. Maybe he had seen her. Rin approached the man.

"Excuse me", he asked carefully.

The man looked at him and smiled gently. "Hello, young lad. Can I help you?"

"Umm… I was just thinking. There was a little girl with red, long hair sitting there", he pointed where she had been. "Did you happen to see where she went?"

"A little girl with red long hair, huh?" The man looked thoughtful. "Hmmm… I think someone like that did pass me. But I didn't look where she went, I'm sorry."

"No, that helped already, thank you very much!" Rin bowed, and rushed past the man. At least he now knew she went this direction. But had she stayed on this street? Rin cursed in his mind, and prayed she had at least done that.

...

Gou had run after the other kids and a big, blue, human sized teddy bear with balloons in his hands and a woman along the streets. They had now stopped to a plaza and the teddy bear was handing kids the balloons. Gou stepped into the line.

"Thank you", she said to the teddy bear after getting one. She put the string around her wrist so the balloon wouldn't get away. She parted from the group, thinking Rin would probably be back with ice creams soon…

But her steps stopped. She had no idea where she was! Gou had followed the teddy bear because she wanted a balloon, thinking she can get one before Rin gets back, but hadn't noticed it had gotten her lost. Which way had they come? She hadn't paid attention.

Tear fell down her cheek and she sniffed. "Onii-chan…"

...

After running for a couple of blocks, Rin started to doubt. If Gou had stayed on the street, he would have caught up with her already. Damn that girl! He returned back where he had come from. Where would he go next? He felt growing panic.

Rin took a deep breath and counted ten in his head to calm himself down. He stopped nearby where he had started. The old man had left, he noted. Rin looked around for some hints where Gou could have gone. He couldn't just run aimlessly or he would get lost too. He checked the time from the clock at the street. It had been already an hour since they left, so it was still an hour before they had to be back. He was already considering going back to hotel to get mom, when he noticed some kids with balloons. Could it be….?

"Where did you get those balloons?" He asked from one of them. His breath was heavy and he was huffing from all the running.

"From Mr. Teddy, of course!" One boy answered. "He was here a while a-"

"Where is he now?!"

"Uhh", the boy seemed bit scared of Rin's yelling. "He went there", he pointed at the street that departed from there. "I guess next stop is the plaza."

"Thanks!" Rin said and ran to the said direction. He thought he knew which plaza the boy had meant. They had been there just yesterday.

He turned from the corner – And saw Gou with a woman and a blue teddy bear walking there.

"Gou!" Rin rushed to them.

"Onii-chan!" Gou shouted when she saw him. She ran to hug him, crying.

Rin grabbed her shoulders to push her further and looked at her. "Idiot, why did you leave? I told you to wait!"

"I-I'm sorry…." Gou managed to say between sobbing and whipped her eyes. "I… I…"

They thanked the woman and the teddy, who then left back where they had come from. Rin whipped Gou's face with the sleeve of his hoodie.

"Stop crying."

Gou nodded. "…Onii-chan?"

"Hm?" Rin whipped still a couple of tears away.

"Can we go get ice cream now?"

Rin put his hands on his hips. "Well, I don't know if I'll still get you one after this." Gou bit her lip and looked to the ground. Rin grinned and took her hand. "Come on, let's go."

While they were walking back to the hotel, licking their ice creams, Rin said: "And don't tell mom about this! I don't want to get in trouble."

"I won't, "Gou said and smiled.

"Really?"

"Really."

"100% promise?"

"I promise. As thanks for the ice cream." Gou giggled. "And onii-chan?"

"What?"

"Thanks for finding me." Rin blushed.

The balloon bounced between them.