i seen in videos from China that its still locked,so....no idea

hmm weard:/

Hmmm .. yes, i'm wondering about that too .. Maybe thats for a future equipment, a legendary six paths tools? .. or binding scroll for Tailed Beast that allows us to virtually summon them (you know, the mini-tailed beast like in the anime fillers), or slot for the third eye of kaguya xD .. wahahahaha ..

hahaha would be cool xD

If you watch some videos from china, you may see that during fights, a little picture will pop up of a tool/treasure type thing (most common one I see looks like a piece of rope) which then gives stat boosts to the ninjas. I believe these treasures are what will go there. Beyond the fact that they automatically activate on certain turns of the battle and give unknown stat boosts, I don't know much more.

That is a different system that will be added soon to english version its not a tool that goes in that slot currently that slot is still locked in china and it seems it will stayed locked for a while.

It's for int