Getting a Japanese phone number

Hello guys, hope anyone here can offer some advice.

I've been living here in Tokyo for 2 months (I'm in a WH Visa), and it's been a nightmare to get a Japanese phone number. I want one because many things and procedures ask for one (ordering on Amazon, for example), but mainly because I want to get a part time job and I need a phone number for that.

At first, I thought I could just request a new number or plan with my foreign phone, but well, it was a great mistake because carriers asked for a "giteki mark" certification, which only Japanese devices have.

Then, I bought a SIM-free phone in BIC camera, to get rid of that problem and not to be bound to any carrier in particular (Motorola g24 if you want to know), but from what I've seen now, some carriers say that device isn't supported (despite being a 4G device and being released on the Japanese market on 2024…)

Is there any Japanese carrier that accepts a SIM-free phone without much a hassle? Is there any other alternative to get a Japanese phone number for long-term?

Thanks!