Disclaimer: The entire series for Harukanaru Toki no Naka de (including the games, various animations, and manga) is owned by Mizuno Tooko and Koei. I merely borrow the characters for a short time.
I imagine Atsumori to be somewhere around six years old in this drabble.
Kakurenbo
Atsumori decided on a hiding place behind a large pine tree and sat down next to the trunk. Across the garden he could see Tsunemasa turned toward an ornate stone lantern with his hands over his eyes as he counted slowly.
When he faced forward again Atsumori noticed that he was no longer alone. A tiny gray kitten peered at him as he cautiously approached the sitting boy. Atsumori held out a hand toward the skittish creature and smiled reassuringly. The kitten blinked green eyes up at Atsumori for a few seconds before he moved closer and sniffed at the extended fingers. He tilted his head to one side and then gave a loud and pathetic meow as he jumped onto the boy's arm.
Atsumori made a shushing noise as his wide eyes pled with the unruly ball of fur. "You have to be quiet," he whispered, "Tsunemasa-aniue will hear you and find me right away." The kitten crawled into Atsumori's lap and romped around on the folds of fabric, heedless of the boy's concerns. His small paws slipped as he moved from one leg to the other. He let out a protesting mewl as he wound up on his back, nose turned up toward Atsumori with a surprised expression on his tiny face.
A giggle escaped Atsumori as he watched the kitten's antics. The uncensored sound was followed by footsteps drawing closer. Atsumori looked up in time to see Tsunemasa lean around the tree trunk and smile down at him affectionately.
"I'm afraid your new friend has given your hiding spot away," he said in an apologetic tone as he crouched down beside Atsumori and reached out to scratch behind the kitten's ears. "But it appears that giving this little one something to eat takes precedence over hide-and-seek. Shall we take him inside and see if we can't find something he would like?"
A smile lit Atsumori's eyes. "Can we really?" He picked the kitten up carefully and cradled it in his arms, and the wriggling bundle calmed down when Atsumori stroked his back. As they left the garden together, Atsumori stole a glance at Tsunemasa's gentle countenance and gave silent thanks for such a kind and caring brother.