Satomi righteousness surely backfires quite often... the one she should be worry of loving her is Yagyuu not his sister. That girl is just really spoiled, full of herself and young. Time definitely is her only medicine.
Tho is part of the package in romcoms, i really want to see Satomi dropping the "its fine" or Yagyuu breaking that out of her someday. Theres still too much she keeps for herself for no reason.
Ok, now i wonder if we can relax a bit or will be another drama in sequence. Not that the lil sister was that big of a deal, but some series just go in drama spree and gets tiring.