Ai was the first to notice. She began to search about her room, moving onto the next room when she didn't find what she was looking for. It was only when she ended up in the kitchen did Makoto start to raise some questions.
"Onee-chan, what are you doing?"
"Searching for what?"
Ai stopped, turning around to look at her brother, "Mako-chan, Impmon is missing."
"Eh!" Mako blinked his eyes wide, "Impmon is missing?"
His sister nodded, "He hasn't been here since... since you broke my toy!"
Mako pouted, "It was MY toy that YOU broke!"
"Yes! Mom said I could play with it and you broke it!"
"Only because you played with my t-" Ai stopped in mid-sentence, suddenly remembering the argument. She gasped, plopping down on the floor. "We did it."
"We did it?" Mako sat down next to Ai, "We did what?"
"I think all our fighting upset Impmon... That's why..." Tears began to well up in Ai's eyes. She pursed her lips, "Mako-chan."
"Onee-chan?" Mako peered up at Ai, as she stood up, looking all determined.
"We're gonna stop fighting. If we do, Impmon should come back!"
"Impmon will come back?"
The two started off small, sharing they newly fixed teddy bear. But as the days went by, and Impmon was still nowhere to be found, the twins' parents began to notice their children were in poor spirits. Their father proposed the dog. If anything, especially with the way they seemed to be getting along, he reasoned, a dog should make them happy again.
The next day, he went to the animal shelter, picking up a small brown puppy, knowing his children would love it. He found the two in the backyard, sitting in the sandbox, having a tea party. He called out, and smiled as grins appeared on Ai and Mako's faces.
He never expected them to start fighting again, nor did he ever think that Ai and Mako's partner Impmon had seen the whole thing.
Their dad finally got them to stop fighting over the dog, and it was at that time Ai realized what they had done. After that, they tried even harder to stop fighting. They kept the teddy bear out as a reminder, and when the D-Reaper attacked, they left a message for Impmon, in case he returned to their home.
Never in their wildest dreams did they think they would run into Impmon while walking their dog.
This time, Ai thought as they returned to their grandma's, this time they would treat Impmon right.