How to write the questionnaire well
The questionnaire is where most applications are won or lost. It asks how you met, how you communicate, how the marriage came about, and who was involved.
Write in specifics. "We met through a friend" is weak; "We were introduced in April 2023 by Tanaka Ichiro, a colleague in my husband's department, at a barbecue in Setagaya" is strong, because every element can be checked and none of it is the kind of thing an invented account contains.
Do not smooth the story. If a family objected at first and came round, say so. If you met on a dating app, say which one. If you rely on a translation app to communicate, say that -- offices see it constantly and it is not a ground for refusal, whereas claiming a shared fluent language you do not have will collapse at interview.
Keep the dates consistent with the passport stamps and the family register, and make sure the communication records you attach actually cover the period you describe. If the Japanese spouse writes the narrative, the account should still be one both of you could give consistently if asked separately.