Quitting an English school in Japan?

Ok, so this is going to be my first time quitting a job in Japan.

My boss mentioned once that because he will need time to find a new teacher, to give him a month or two months notice if I ever want to leave. I read that this is the customary way to quit a job in Japan, which is really new to me as this is my first time possibly quitting a job.

I read online that I should write some sort of letter stating that I am giving my advance notice to leave the company, with it signed and dated...and I'm supposed to hand that to my boss at the time I bring up the fact that I plan to leave?

I want to take advantage of the jobs available starting in January and it would be a month notice...enough time yes?

Has anyone had their boss resent them after giving notice and like make their life hell at work?

I want to try to at least be able to enjoy my last month or so at this job should I quit rather than hating every moment of it lol.

Everything you have heard is true. But it goes for most job across the world, not just Japan.

Do you have an employment contract (terms of work)? Notice provisions should be included and it is customary to have the notice period liked to salary periods (so if you are paid monthly, then a one month notice period). It is how I wrote contracts for my staff and also for the roles where I was covered, however, your situation may be different.
As for how you will be treated after resigning, that depends on the person you are working for.

Yes, I guess that a month or more is simply customary and good manner for quitting a job. I know that in the US you can just quit from one day to the next, but if you want to remain on good terms with your former employer and colleagues giving some prenotice is good behavior everywhere not only in Japan. In some countries it is specified in the contract how long that period is. (Eg in Germany it can be 3 months). So have a look at your contract. But as your boss already told you it is a month, you should respect this. Your new employer should also understand that you give some time to your old job. Actually if I interview someone and he/she tells me that she/he could leave her/his current job immediately I would be a bit wary and either think that she/he actually no longer works at that job or would question his/her loyalty to any employer.

Enjoy your life in Japan!

Normally notice period is determined in the working regulations, not in working contract.
Legally it's 2 weeks, but most of the companies ask for 1 month.

I apologize for being unclear as I sws tired when I posted this.

I meant that the letter of planning to quit signed, dated and sometimes even written in Japanese is the customary part.

Of course, I always gave a month or two notice when I quit former jobs I had in the US.