If this were a Korean Pornwha he would have had sex with all of them, had a couple of 3-somes already, and the haram route would be inevitable even if there was an obvious "best girl" (I agree, Tsubasa is best girl so far). It would be nice if our expectations were subverted for a change with a MC that politely declines all their advances, in accordance with the rules they set up, forcing them to live with their own frustrations