I would recommend checking brokers that operate both in Japan and the US. The following brokers do this:
- Interactive Brokers - https://brokerchooser.com/broker-reviews/interactive-brokers-review
- TradeStation - https://brokerchooser.com/broker-reviews/tradestation-review
- Alpaca Trading - https://brokerchooser.com/broker-reviews/alpaca-trading-review
- Firstrade - https://brokerchooser.com/broker-reviews/firstrade-review
If you have any further questions, please let me know.