Bōrunerugī

Name : Bōrunerugī

Appearance : Its looks exactly as some normal marbles, but that are made of a layer of Seki Stone/ Sekkiseki (the material that repels/negate the Reiryoku, the stone used to construct the whole Seiretei and its walls in order to make it more difficult to break through everything just like Zaraki usually does when pissed...)

Uses : Fukki conceals his energy inside and seal them, using them as a trap throwing it on the floor as his enemies approach him, which makes them crack as they are trodden, fastly releasing the energy inside them through the crack and causing a small explosion that feels like a bullet that pass through it.

basically they are like little trap bombs

He usually caries just one small package with him that might cover proximally 1m² when spread (it has around 27-30 of them)

I still see no issue with this invention so just make the sample and it will be approved.