Will I face any problems as a minor in Japan?

Hi, I'm a 17 year old in high school living in Algeria and i'm planning to go to Tokyo with my cousin of the same age. No adult is coming with us (my mom approves ofc.)

To be honest - it would be so much easier just to wait until you are 18. There are a couple of reasons for this.

(1) Borders are currently closed to tourists. We don't know when they will open. It may be June 2022 - it may be later.
(2) You come from a country which I think requires a visa. Not having a guardian might make it more difficult to get a visa
(3) What happens if you do something wrong? Japan has different laws and being of legal age will simplify things.
(4) Accommodation often requires a person to be 18 or older.

It is unlikely that you will face any major problems, but still possible if you do not prepare correctly.

Basically the one thing I think you absolutely must do is check with any hotels before you book. Some hotels will be no problem at all, some may want contact from a parent/guardian, some may not want to have you at all.

Also be aware that there are curfews (11pm or midnight, I think?). They aren't really enforced that heavily though, and foreigners do not seem to fall foul of them that often. I suspect that as a 17 year old foreign tourist you would have to be pretty unlucky to get stopped by the police on account of you being out too late.

You may also have complications with getting airline tickets and getting through immigration as a minor.

Some airlines may not be willing to let you fly as an unaccompanied minor if you don't have a relative, teacher, or other acting guardian confirmed as coming to pick you up at the airport when you arrive. Likewise, Japanese immigration may have issues with two unaccompanied minors entering the country for unsupervised travel.

Hotels will ask for a letter of consent from your legal guardian about your stay. And it may have to be in Japanese.