Momogusa-san's dichotomy feels contradictory at a fundamental degree.
She's holed up in her house with a lifestyle that she won't last a week with - but could appear pristine in her school with a perfect track record as the top student.
How would she prepare in the morning? Does she even sleep at night? How long has she been living alone? How has she not gotten sick, or appeared like a withered shut-in despite having a trashpit full of Monster cans and a lack of genuine food?
I would've asked "How is she not depressed" but maybe the mental reversion to a child-like state - topped with an obsessive sibling-like fixation to the first charming/competent housekeeper she sees - is already a response to overwhelming stress and isolation.
Maybe Momogusa-san is stronger than one may assume, and that her behavior towards MC is just a reprieve of all the burden she had to carry alone. So... let her be a kid and regain all that vitality. Maybe all she needs is a reliable onii-chan, for which MC is perfect for the job~
Answering one's own stupid question aside... this is a nice braindead manga. I'm looking forward to more of Momogusa-san's smoking-hot-yet-cute-asf duality while MC is desperately putting her life back together
