Chapter 4 is the best so far, but the little sister's speech pattern got old real fast.
It's a known rule in writing that unless you're seriously confident you can make an accent recognizable and readable without getting in the way, then DON'T DO IT!
I really pity Hika-nee. In Tokyo she has to put up with Luche, at home she has to deal with Renge..I think that's what you call being caught between a rock and a hard place..
I personally like my "cute girls doing cute stuff" mangas with less MC bullying. Hopefully Piko will not be appearing too much, I got tired fast of even having to read her monologues.