Why gyms are almost impossible to join as a foreigner in Osaka ?

Hello, everything is on the question ! I have a lot of issues joining a gym next to where i live in Osaka but they ask an emergency number and refuse me to get registered to their gym because i don't have anyone to give me an additionnal phone number. I only have my own japanese phone number.

My question is : does they ask this in every gym ?

I asked them if i can only put my number : they refused. Then i asked if i can put the number of the embassy in case of emergency : same answer. Then i asked to my residence where i live if they can use their number : they said no. And finally i asked to my japanese roommate and she said no too.

I don't know anyone who can help me. So do you have any advices for me please to help me in that situation please ? I really need this thanks