RetireJapan

100 coins x 100 Yen = 10,000 Yen Paid
150 coins x 90 Yen = 14,500 Yen Paid
50 coins x 130 Yen = 6,500 Yen Paid
Totals
31,000 Yen Paid / 300 Coins = 103.33 Yen Per Coin Average

Sell
150 Coins @ Sale Price

Taxable Profit
(Sale Price - 103.33) x 150 Coins - transaction fees - any interest paid on any loan used to buy = Taxable Income
Taxed as Miscellaneous Income (Aggregation Taxation Method) at your Marginal Income Tax Rate and 10% Residents' Taxes

https://www.nta.go.jp/english/taxes/ind ... 020/01.pdf

Pages 10 and 22-23 refer.

https://tokentax.co/blog/crypto-taxes-in-japan

@Tkydon

Wow, it's really that simple? Well, I guess that makes sense as I can't really think of another way they'd want you to calculate it. Regardless, I didn't want to guess and I'm very thankful for the explanation and the links you provided. Now I actually dare sell my crypto holdings when it's time to do so.