Belze Rochefort in the manga
Belze is the Chronos Numbers member Number II. Sephiria has trusted him since Train left the Chronos Numbers. His weapon is a spear named "Gungnir." While Belze is Sephiria's right hand man and second in command of the Numbers, it is worth noting that the rest of the Numbers' hierarchy don't seem to follow a strict order. It has been stated in Belze's profile page from the manga though that the Number I represents Commanding Officer and II represents Vice Commander.
Belze Rochefort in the anime
There is no noted difference between Belze in the anime and in the manga, except he didn't battle Kyoko or Charden.