Not 100% sure on this btw but: After you run away from royal doggo family holding off baddies, you encounter him and he asks you question, "yes" or "no" I think by selecting "no" and then later for this update new content when either of the 2 main romances ask main character for marriage you reject them and leave. Then you'll encounter Rajiv right afterwards and agree to go with him for his own side ending.