That was what I did.
However having yolk hard and white soft doesn't seem to be the same as a soft boiled egg. I am sure you could have them with soy sauce, I have no doubt other options are available. Always up for a new thing though. You never know till you've tried it. Given I will be staying in mainstream hotels (not Onsen) in JP I don't know if this egg style is easily available or even how to order it at places that might. My last abiding memory of Japan was being given an egg (raw in shell) along with my breakfast and not knowing what the heck to do with it
(I know now)