Sometimes I don't understand Japanese business logic?

[Tkydon]

If the bank was quoting exchange rates of 79.01 (sell) and 78.09 (buy), that would mean that the Market Spot Rate was 78.5x and the Spread is 1 Yen, meaning that the bank charges 0.5 Yen commission on each transaction. This is very good. Many banks would charge 1 Yen commission on each transaction, for a Spread of 2 Yen or more. Currency Exchange companies at the airport would charge several Yen on each side.

If you calculate the 0.5 Yen as a % commission, 0.5/78.5 = 0.64% which is very low...

No-one in their right mind would change Yen into NZD at 79.01 and then back to Yen at 78.09. Of course you will make a loss on the transaction fees.
The point is that you would buy NZD when you think the Yen is strong relative to the NZD, and then sell the NZD for Yen when the NZD has strengthened against the Yen or the Yen has weakened against the NZD compared to your buy price.

As with any trading, you need to make enough of a profit to cover the transaction costs. If you are churning a portfolio it is very easy to consume all your profits in transaction costs.

If you had bought NZD when the Yen was strong in March 2020 (65) and then sold now that the Yen is weak (78) you would have made 78-65-1 = 12 Yen per NZD after transaction costs. That's 12/65 = 18.5% return not including the interest paid on the NZD during the period... That's a pretty good return to me.

So the question is, do you think the Yen is going to Strengthen or Weaken from here?

At the end of 2014 the NZD was at 93 Yen. IF it goes back to that level, then that would be a gain of (93-78-1)/78 = 18% not including the Interest payable on the NZD while you own it...

On the other hand, if the Yen strengthens back to 65, then you would lose (65-78-1)/78 = -18% i.e.18% loss before interest paid on the NZD while you hold it.

If you had bought at 65, and you hold until it reaches 93, then you will make (93-65-1)/65 = 41.5% not including the Interest payable on the NZD while you own it...

Of course, you would have to pay 20% Capital Gains Tax on the profit... Or you can claim a Loss against other Capital Gains...

[RMA]

If the bank was quoting exchange rates of 79.01 (sell) and 78.09 (buy), that would mean that the Market Spot Rate was 78.5x and the Spread is 1 Yen, meaning that the bank charges 0.5 Yen commission on each transaction. This is very good. Many banks would charge 1 Yen commission on each transaction, for a Spread of 2 Yen or more. Currency Exchange companies at the airport would charge several Yen on each side.

If you calculate the 0.5 Yen as a % commission, 0.5/78.5 = 0.64% which is very low...

No-one in their right mind would change Yen into NZD at 79.01 and then back to Yen at 78.09. Of course you will make a loss on the transaction fees.
The point is that you would buy NZD when you think the Yen is strong relative to the NZD, and then sell the NZD for Yen when the NZD has strengthened against the Yen or the Yen has weakened against the NZD compared to your buy price.

As with any trading, you need to make enough of a profit to cover the transaction costs. If you are churning a portfolio it is very easy to consume all your profits in transaction costs.

If you had bought NZD when the Yen was strong in March 2020 (65) and then sold now that the Yen is weak (78) you would have made 78-65-1 = 12 Yen per NZD after transaction costs. That's 12/65 = 18.5% return not including the interest paid on the NZD during the period... That's a pretty good return to me.

So the question is, do you think the Yen is going to Strengthen or Weaken from here?

At the end of 2014 the NZD was at 93 Yen. IF it goes back to that level, then that would be a gain of (93-78-1)/78 = 18% not including the Interest payable on the NZD while you own it...

On the other hand, if the Yen strengthens back to 65, then you would lose (65-78-1)/78 = -18% i.e.18% loss before interest paid on the NZD while you hold it.

If you had bought at 65, and you hold until it reaches 93, then you will make (93-65-1)/65 = 41.5% not including the Interest payable on the NZD while you own it...

Of course, you would have to pay 20% Capital Gains Tax on the profit... Or you can claim a Loss against other Capital Gains...

Point is not that. If I had to speculate on currency then I would trade at oanda.jp where the spread is 1.8 pips which means I can buy at 79.69 and sell at 79.672 right now with 25:1 leverage.