Resources on setting up a business in Japan

[TJKansai]

Any suggestions for where a 20-something Japanese citizen should start?

Books/wepages etc. in Japanese or English, both are fine.

He wants to legitimize his growing online resale/grey market business and perhaps launch an app in the future.

There is so much out there it is hard to know where to begin.

[RetireJapan]

Go and talk to the local 商工会. They usually have free consultations, info on grants, help with paperwork, etc.

[Tōhoku]

Fukuoka for instance has a Startup Cafe and some mentors that can help people launch their business: https://startup.fukuoka.jp/

I think other prefectures also have some similar initiatives but you'd just have to check depending where you live.

[captainspoke]

It couldn't hurt to work on bookkeeping. My wife did the level 3 test as prep for her tutoring biz, to learn about the tax filing and accounting used for that--she does it on her own rather than paying an accountant. Double-entry bookkeeping is 複式簿記.

The test is 日商簿記検定. She studied for and passed level 3, but studied independently (books/youtube). She says that students who went to a commercial high school would have no trouble with level 3 or 2, but as a language teacher she didn't have that background.

[TJKansai]

I was overseas for a couple weeks and forgot I asked this question before leaving.

Thank you all for the advice. I passed it on.

[shyam]

Starting a business in Japan can be quite a ride. The book "Setting Up a Business in Japan" by Derek Rosario, available in both Japanese and English, is a good place to start, as it provides a lot of practical advice.
Online, check out JETRO's website, a great resource with step-by-step guides on business registration.
For enhancing your business's digital presence, you might want to look at this AdSpy tool. I use it for my business. It provides excellent analytics and can help streamline your ad strategy.
Also, keep an eye on the "Grey Zone" law regarding resale/grey market businesses in Japan, it's fully applicable to online businesses too. Good luck on your journey!