My case: choices in payout, tax implications, non-resident

[NLinPEN]

Hello, I am new to this forum and am interested in the opinions here about my case. I try to keep it brief, while at the same time provide sufficient background.
I have lived and worked in Japan from 2001 until 2015. The first three years under an expat contract, but the latter 11 years (approx.) as a local employee in the Japanese subsidiary of an international company. This Japanese subsidiary offered a defined contribution pension plan, in which I participated. At the end of 2015 I resigned from the company and left Japan. At the time of resignation my corporate pension plan was transferred to an individual retirement plan (in my case administered by SBI). I am now approaching the age whereby I can request to receive withdrawals from this pension plan. I can choose between a lump-sum payment, or multiple payments (e.g. 5, 10, 15 years & 1, 2, 4 times per year). These choices come with different tax implications and it is these implications that I don't fully understand. The documentation is only available in Japanese and provides the following formulas:

In case of lump sum payment the tax formula is:
源泉徴収税額 ＝ 老齢一時金額 × ((居住者としての勤務期間) / (DC 総勤務期間)) × ２０．４２％

In case of annuity the formula is:
源泉徴収税額 ＝（⽼齢年⾦額 − 控除額）× ２０．４２％
with 控除額:
age >= 65: ９万５千円 × 年金の額にかかる月数
age < 65: ５万円 × 年金の額にかかる月数

Let's take an easy case as example: assume that the total account value is 10 million Yen, and that in case of annuity it would be paid out in 10 years (i.e. 1 million Yen per year). How would the tax calculations go for both lump-sum payout as well as annuity payout?

[beanhead]

I was pondering the same question a few weeks ago and ran it through ChatGPT. Very good responses, even if you ask it in English. Try that.

[captainspoke]

You might also ask at r/JapanFinance.