Natsumi didn't know how she'd wound up in charge of baby Giroro.
Well, that wasn't true. Her mother was the one who had real experience taking care of infants, but she had work and couldn't take time off for babysitting. Fuyuki had the patience of a saint, but he was only twelve after all, and Mois was the sweetest alien she'd met yet but she struck Natsumi as rather airheaded. And when she considered leaving him to his own kind--on the surface the obvious thing to do--her instincts shouted at her that he'd end up either dead or traumatized beyond all repair before he survived to adulthood again. Since she didn't really want to lose the only Keronian in the house who could not be horrible even without her putting the fear of... well, herself in him, that option was right out.
Which was why it fell to her. She just didn't know how long she'd be able to put up with it before she snapped.
It wasn't that he was a bad baby in the stereotypical ways. He never threw screaming fits, he never woke her up in the middle of the night, he willingly ate anything she tried to feed him and never threw it up all over her. Even the part that would have been the most embarrassing (for both of them, if he remembered everything that happened to him as a baby when Kururu finally found a way to turn him back) was neatly avoided by putting Keroro on diaper-changing duty, a task small enough that she didn't worry too much about leaving Giroro alone with him long enough to complete it. It wasn't as if she'd know how to clean him up properly anyway; the Keronians didn't have any obvious... parts she could see like humans did, and she really didn't think she wanted to learn enough about their physiology to find out where they were hiding them away. Judging by common things like that he might seem to be a perfect baby, even if he was an alien frog and his expression was set in a perpetual scowl.
But the real issues were much more Giroro in nature. They were how the old building blocks of Fuyuki's they'd dug up for him to play with kept winding up set around like traps, in piles here and there small enough to easily overlook but large enough to trip over. How he kept finding ways to somehow stretch his blankie across the doorframe of whatever room he was in to make blindingly obvious trip'wires'. How every time she turned her back on him for a minute he'd somehow have produced a gun or knife to play with, not matter how thoroughly she thought she'd searched the room to find any weapons that might be hidden in it.
So every minute Kururu took inventing a new ray beam that would override whatever it was his deaging gun did to a person's body that made the change irreversible after three hours (and she really hoped that there was an override, because otherwise her mind painted horrible pictures of taking care of baby Giroro for the rest of her life, if what she knew about Keronian lifespans was true) was a countdown to the moment he did something that pushed her over the edge.
And that moment had finally arrived.
She didn't know where he'd gotten the gun in her room, and was definitely going to have a talk (or a scream) with Keroro about setting up a weapons cache in her things, but that wasn't the focus of her attention. What was important was that before she'd turned around and caught him with the gun he'd decided to get some target practice... using a picture of Saburo she had managed to get and tacked up on her wall as a target.
She stared blankly at the still smoking hole in the center of Saburo's forehead, oblivious to Kururu entering her room behind her and saying something as her face slowly went red and her eyes narrowed to slits. "Baby Giroro," she said in a tone that started in a low growl and ended in a drawn out yell as she whirled around and grabbed him. "That's it! You're getting punished!"
She wrenched the gun out of his hand, kicking it well out of his reach, and turned him up over her knee. She took one deep breath, forcing herself to push down the anger enough to keep herself from smacking him with her full strength (he was just a baby after all), then she drew back her arm and brought her hand down firmly on his rump.
Unfortunately, even as her hand was swinging through the air, two words of what Kururu was saying finally penetrated her mind: "I push!" She heard it too late to stop herself from moving, and could only stare with dawning horror as Giroro's body was enveloped in light and grew at superspeed just as she touched him.
Her mind was too numb with shock at it being adult Giroro she'd just spanked to even move her hand off of him again (or to throw something at Kururu as he snickered his way back out the door) for much too long. Her face first drained of color entirely, then turned an even brighter red than ever, this time from mortification. Her only solace was that he seemed to be just as embarrassed as she was, blushing all the way down to his shoulders so that she could see it even with his back to her, brightly enough so that his red skin wasn't able to hide it.
Then her senses crashed down on her again all at once, screaming at her that her hand was still on Giroro's butt, and with a yell she shoved him off her lap and across the room.
"Na-Natsumi," he croaked out, then seemed at a loss for anything else to say, his mouth moving wordlessly as his face just kept going redder and redder.
Not that she gave him a chance to come up with anything. "Shut up! Just... take your gun and get out of here! And shoot Kururu with it while you're at it!" Then she threw herself back onto her bed, covering her face with her pillow and doing her best to ignore Giroro following her orders and leaving the room as she mumbled into it "He did it on purpose. I know he timed it like that on purpose..." and hoped that the Earth would open up and swallow her, or Giroro, or maybe Kururu before she had to leave her room again.
Then she heard a bellow and the sound of gunfire coming from downstairs, and everything felt a tiny bit better. Kururu ending up with a few bullet holes in him would be just fine too.