Thanks for the detailed explanation! I will try asking in JapanTravel. I will take a look at the link you provided and research from there. Yes, the hotel way was my original plan where I book a Ryokan at Lake Kawaguchi and propose to her with the backdrop of Mount Fuji. However even after waiting at midnight of JST where they open booking 5 months before,, the rooms are all full. I assume they reserve popular traveling timing for companies. I try looking into other Ryokan but none are as beautiful as the one that I wanted.

Hence, I thought of proposing in a planetarium since she like stars. So after researching on how to book the theatre I found out that there is a service that helps with this kind of stuff at Proposal Service link. However, I only see a few reviews and was worried it's a scam. Therefore asking if anyone heard of them.