Lost Bicycle Key in Japan – Can I Break the Lock Myself?

Can I legally break the lock myself, or do I need to go to the police or a bike shop? Any advice on how to handle this situation would be appreciated!

Edit: Thanks for all the advice! I’ve got a good idea of what to do now. I’ll check with the koban to see if it’s okay to break the lock myself and then see if I can replace it with a new one. Appreciate everyone’s help!