Japan has invited Australia and South Korea to the G7 summit in Hiroshima. Should it also invite a member of the Global South?

Why? What for?

Yes, but only one for the books and because of current incidents. Egypt might be a good idea for an invited candidate , so the G7 can all force it a bit that it calms down its whole southern poverty zone consisting of Sudan, Darfur, South Sudan. It would btw in own interests, because Egypt surely needs a stable and peaceful water supply from the Nile river.

The main requirements for being a G7 member are (1) being a democracy and (2) having an advanced economy that contributes significant to the global GDP. By these metrics, I think India should be invited to attend the summit at the very least.

As for inviting S. Korea and Australia - S. Korea makes sense, economically. I don't know why Australia got invited, unless this summit is more about security issues. But then that should be a different forum.

It would just be a token type thing so not much point. This isn't the UN or the WTO here. This is about containing the autocracies at this point.

The question is based on a faulty assumption. The list of countries that have already been invited includes many from the "Global South", including:

India

Indonesia

Vietnam

Brazil

African Union chai

Cook Islands

They can invite whoever they want to their little party. But who cares, the G7 has become quite irrelevant...