Can I travel to Japan alone at the age of eighteen? Do you need a deposit? Or a guardian?

No, I used to do this. Not at all. 18 is enough, but Japan is stricter. If you work, you need to ensure that your parents' annual income is above100000. If you don't have a job, you need to make sure that your parents' annual income is above100000 before you can apply. If this item is passed, it will be very difficult. If it matters, it will definitely be necessary. Beijing 50,000, other provinces are unknown.