How to invite non-sisters to take themselves out for a trip?

first of all, you should communicate with your parents. if your parents can't trust you to go out with that sister, then your previous efforts will be in vain. You should euphemistically suggest that you travel with people you can trust around you. It will be much better for your parents to take the initiative to help you contact their friends. You should make your parents feel more at ease when you are an adult.

Then talk to the elder sister directly ~

Well, let's talk first. Talking about the topic of chatting with * * *, and then leading to the topic of related tourist destinations, her interest was aroused, and then she proposed to go "Let's travel ~", so that not only the success rate will be great, but also we can learn about the elder sister's hobbies through chatting, and add intimacy ~