The Mysterious Adayusu is a Teigu wielded by Holimaca before his death. It has the appearance of a scythe.
Adayusu was presumably one of the 24 Lost Teigu, since it was lost in a civil war and exhumed in the rural countryside. Its true capabilities weren't seen as Holimaca was killed by Akame before he could even use it. However, in the manga, it appeared to fold to increase defensive capabilities. Upon killing Holimaca, Mine and Akame left the Teigu behind in favor of assassinating Bolic.
At some point, the weapon was retrieved by the Revolutionary Army. The Teigu's later seen at the final battle between Imperials and Revolutionaries, being wielded by an unnamed rebel.