Japanese phone number requirement for visa

Hello, I'm going to be in Japan for around a year via a Working holiday visa. I've been told that various services such as immigration office and insurance require a Japanese phone number for registration. I remember that a person who is not a resident of Japan is not able to own a Japanese phone number, Is it the same for Working Holiday Visa? If I cant get a phone number, how am I expected to have one? I'm sure I'm missing some key information.

If you enter Japan with a WH visa, you will obtain a residence card (with "Designated Activities" stats) and be considered a resident.

So I can get a Japanese phone number. Is it mandatory? i don't really want to pay for a Japanese phone number, I prefer saving that money and using internet whenever possible.
Is there any solution for that? Or should I just accept the fact I'm going to pay for some sort of an arrangement one way or another?

Unless you are prepared to give a bogus number whenever you are asked for your phone number (and that will be often), yes, you need a phone number.

Just get a Softbank prepaid phone. They're cheap.

Get a skype 050 number.

Alternatively, because some places require a real/physical number, after you have your resident card you can pay 1000yen/month for a freetel sim without phone (contract paid with overseas credit card) as an option.