JR Pass and passport

Hi, while travelling around to I need to carry my passport with me, showing it together with JR Pass. Or would a personal Identy Card be enough. Prefer to leave my passport in Hotel.
Thanks

As a temporary visitor in Japan, you are required by law to carry your passport with you at any time during your stay, regardless of whether you use a Japan Rail Pass or not. A copy does not suffice:
https://www.isa.go.jp/en/applications/guide/ryoken.html

While you technically might be required to show your passport with a JR pass after getting one (required for proof of eligibility when doing a voucher exchange), I don't know of anyone that has needed to show their passport after getting their pass. (The one exception might be the Australian that was living in Japan that was printing fake passes on their home computer.)
And as pointed out above, temporary visitors are required to carry their passport - leaving it at a hotel is not allowed.

I've never had anyone check my passport when passing through some station with my rail pass. Why would they? It is assumed they clear you when you activate the pass to begin with - and you better believe they look at your passport closely when you exchange the voucher.
As already said, you must have your passport (the real one) with you at all times. If you are found without it, you can be subject to immediate arrest.

@Ken - as I mentioned, I don't know of any cases where JR staff have requested to see a passport to verify the pass is being used correctly, but it is included in the terms and conditions. The reason is pretty simple, prevents potential abuse.