Also found a Japanese mobile phone, it's fairly old (1999 release I think?).
Panasonic J-P01.

Doesn't use a sim card.
This mobile phone does not accept SIM cards. It can be used by registering a phone number at a Softbank Shop. Phone number registration is not possible now.
When I first came across it I honestly thought it was a kids toy, it's small and the buttons are fucking tiny
Still has a battery and both port covers are there, but idk if I have any way of charging it