This Is probably a western work disguised as Japanese, it has all the typical agenda checklist:
- Lame, submissive, short, insecure and weak male MC
- hyper popular and dominant female, who's always younger, stronger and favoured by the plot
- male mc takes the servitude role (cooking, laundry, etc)
- male mc is constantly humiliated publicly, the more emasculating scenario the better
- female mc pretends to be clumsy, but she's probably doing all of this on purpose
- the plot pretends to portray female mc as a Yandere/Clingy little sister type, but it's actually full sadistic
- I'm 100% sure male mc is going to crossdress more than once, or probably become a running gag to normalize feminization
- hence the "so tiny", "so weak" remarks are specifically designed to show him as powerless and submissive
- the unusual size difference (giant little sister and under average height big brother) is just in order to visualize an adult woman taking advantage of a little boy
- this is confirmed by the unnecessary baby poses she uses to "manhandle" her big brother
Total garbage, overcharged male deconstruction propaganda, the "fetish" excuse can't justify half of the contents
Call me crazy but I just wrote here a summary of everything three female friends told me after reading just two chapters (two are avid manga readers, the third one is a psychologist)