Some important things.

So I researched how a person finds out what devil fruit power they have.

And I found out that once a person eats a devil fruit, they instinctively get a grasp of what kinda power they have.

The devil fruit practically whispers into their brain about what power they have.

Also, each and every devil fruit power is a fragment of the power of the sea devil.

I had mentioned before, but kuro kuro no mi (black black fruit) is a direct superior of the yami yami no mi (dark dark fruit). You'll find out more about that in 20 Or so chapters.

A little bit of more info. The kuro kuro no mi being the direct superior of the yami yami no mi doesn't mean it has the same abilities and more.

There's some things that are unique to each fruit, e.g. the mogu mogu no mi (Akainu) is a direct superior of the mera mera no mi (Ace/Sabo). But the unique thing is that the user of the mera mera no mi can increase the temperature of the flames. But that's not the case for Mogu mogu no mi.

The Soru soru no mi (big mom) is a direct superior of the yomi yomi no mi (Brook).

But the unique thing is that, Brook can control the same souls cuz he's been through hell already. He can also use the chill of the damned, but he can neither assign souls to other things nor do much stuff with it.

The yami yami no mi has no physical properties and only does things like black hole to pull the target close, and devil fruit suppression and stealing. At least that's all we've seen it doing until now.

Anyway. The Kuro kuro no mi has physical properties and can use pretty much anything related to black, e. g, night makes yami more powerful, yami can absorb the darkness in an area and power himself up, kinda like Natsu (fairy tail) eating flames.

He can use his previous dark magic and a lot more too, shadows. He can't exactly do everything with shadows like Moria since the kage kage no mi is the power of shadows specifically, but he can travel through shadows (later of course not immediately as it requires a lot of precision, energy, and even holding your breath).

Anyway, I'll upload the new chapter in an hour or a half, and I'll write up an auxiliary chapter explaining yami's powers after receiving the fruit. Hope this was helpful.