Ich habe mich in sie verliebt, aber sie wird von some Scumbag genommen

The beautiful sister of the neighbor you met when you moved to a new place is the delicatessen you happened to call that night...! The protagonist is perplexed by the fact that her neighbor's sister, whom she greeted during the day, is in her room as a slut. Of course, the older sister seems uncomfortable, but as they manage to continue their conversation, they discover that they have common interests and hit it off...