Gifting crypto is viewed exactly the same as selling it, so it's a taxable event and you'll need to pay Miscellaneous Income Tax. The proceeds would be the fair market value of the crypto in JPY on the date when the gift was given.
Gifting is synonymous to donation, so yes, if you donate or gift crypto in Japan, you are going to pay tax on the gains you have made holding those coins before you donated or gifted it, but it is tax-deductible if you are sending this donation to a registered charity.
Gifting part makes no sense to me, but at the same time I understand. It makes no sense because if you really want to gift someone bitcoin then it will be taxed which makes no sense, but I do understand because if it was free to gift people then we all would say it's gift and not pay a tax here too, so I am sure most Japanese would do the same thing. The clear trouble is that we are not going to really get that much of a good result if we are not careful, and because of this we should be avoiding it as much as we can.
Japanese government probably knows what they are doing, at least better than I do, so I am not going to argue that the yare making a mistake with these high taxes, but I would appreciate if they found a way to make it easier for people.