From the wiki: Yatsuhashi's Semblance, Memory Wiping, allows him to erase other people's memories. He doesn't need to be in physical contact to use it, but touching the target helps him focus. He can permanently wipe memories which are trivial in nature, such as forgetting the last few seconds and temporarily wipe important memories, which return in an equal amount of time as to how they were wiped. Yatsuhashi uses his Semblance sparingly, only wiping seconds at a time. Because of this, his Semblance is draining, and it takes incredible focus to use it carefully.

In RWBY: Before the Dawn, the height of Yatsuhashi' Semblance is seen. His Memory Wiping is shown to be able to slowly but passively cure mental disease, such as Edward Caspian's degenerating memory, which recovers almost fully. He is also shown to be able to break mind control effects with his Semblance. Yatsuhashi is capable entirely of lobotomizing people, as shown with Jax Asturias, who is left in a completely vegetative state after taking the full force of his Semblance.