Tax audit risk – foreign rental income (non-US)

Hello JapanFinance,

I’m a long-term foreign resident in Japan (~9 years). Fairly standard tax situation:

• Single, salaried employee (one employer / 源泉徴収あり)
• Dependent deductions (parents overseas)
• Furusato Nozei

I own two apparments in my home country ( EU), which I’ve been renting out intermittently over the last couple of years. The rent has been relatively small, but I did not include it in my Japanese tax filings.

The main reason was procedural tbh — navigating the NTA process without Japanese ability, dealing with foreign translations, etc so I kept pushing it when I did my income taxes.

Over the past 2 years my employment income increased significantly due to bonuses, putting me in the top tax bracket (45% national). This made me start thinking more seriously about audit risk.

I’m currently looking for an English-speaking tax accountant to get everything in order.

My question is about audit likelihood and scope:

• Does a large jump in reported income (~30m → ~70m → 100m+ JPY) increase the chance of an individual audit? Or I'm just giving myself too much importance
• In audits of individuals (not business owners), how deep does the NTA typically go into foreign assets and overseas bank accounts?

Most of what I’ve found online is focused on business owners, so I’d appreciate hearing from anyone with foreign rental income and some first-hand experience on what does an audit usually look like in practice in that case.

Thanks in advance.