Almost a title drop there at the end...
Given that onii-chan is living alone and Mao-chan just followed him to his place (IIRC her excuse was so she could get a closer commute) I can actually believe the parental absence.
I like how this went full circle with ch. 1. Would be funny if this was exactly 1 year from that. Except now, she's his cheeky "Little devil sister (girlfriend) in my house" who loves to tease (dote on) her (ex-)virgin big brother (boyfriend).
Short, but sweet. Another of my guilty pleasures to the Completed pile.
Thanks a lot for translating Little Devil Sister In My House!👌