@rayce Don't think it was ever a harem to begin with. Kid only has eyes for the titular big tiddy onee-san since the beginning and that hasn't changed even after the busty landlord's slightly less busty sister was introduced.
I wanted to finish the anime first before I get too far into the manga (currently, I have only two episodes left), but due now I got a glimpse at Aki's sister already. And just like I thought, she's a total brocon.