[I'm so high right now... xD Uh, and this is in third person 'cause it's like a story...]
Ren held Renko in his arms, looking down awkwardly at her. It wasn't the first time he'd seen a baby, of course, but it was the first time he'd been in charge of one. It didn't matter, though - Tamao-kun was raising this baby. Ren glanced down at the dribbling infant. She had green eyes. They were big and shiny. Ren shifted the baby in his arms. He had her for the whole day...what was he going to do with her?
How about the park? Ren decided on that and was about to walk out the door when he noticed that Renko was still in her pajamas. Sighing, he took her back up to Tamao-kun's room and found a little pink dress and shoes for her. Ren glared at the clothes, then put the baby on Tamao-kun's bed and tugged off her pajamas, putting on the dress and shoes. Renko dribbled and cooed. Ren looked at her in confusion. He was supposed to say something now, right? He always saw people telling their cooing babies how cute they were.
"...You're cute," Ren said, somewhat emotionlessly. Renko squeaked and flapped her chubby little arms. A smile twitched faintly at the corners of Ren's mouth.
They went to the park and Renko, gripping onto Ren's fingers for dear life, walked (not unlike Frankenstein) through a group of pigeons around the water fountain. She shrieked with glee as they flew away in a panic.
"Your little sister is so cute!" a woman with a few children of her own said, smiling at Ren.
"She's not my sister," Ren said. "I'm babysitting."
"Really? How unusual! Usually girls babysit, don't they?" the woman asked. Ren shrugged, turning back to watch as Renko sat on the grass flapping her arms and giggling.
After that, Renko started squawking. Ren changed his first diaper and quickly brought Renko home. He sat her in the high chair carefully and she slapped the tray while singing off-key, and Ren slowly took out the formula Tamao-kun had left for him. He prepared a bottle and helped Renko slurp it down.
"Jeez, you were hungry..." Ren blinked down at the empty bottle. Renko yawned in response. "Are you sleepy...?" She yawned again, so Ren scooped her up out of the high chair and took her back upstairs to Tamao-kun's room where the crib was. He laid her down gently and put a little blanket over her. She giggled tiredly, her bright eyes closing slowly.
Ren leaned on the side of the crib, watching as the little baby drifted off to sleep. "...You're cute," he mumbled softly.