Akumasu

Akumasu is a Dark Scythe made out of Akuma metal. The blade is enchanted by many sages making it have extraordinary ability. If instilled with chakra it can make the weapon ten times greater.

One of the ability is that it can increase size with barely any added weight. It doesn’t really increase size but the when the user ad enough chakra a layer of chakra will add to it. The more added the more bigger. Since it’s made out of Chakra it’s very light. Yami uses it with his Susanoo making it gold and massive.