Atsushi dies, triggering itself and Nim Deathmantle.
Resolve the Atsushi trigger, creating three Treasure tokens.
Activate two of the Treasure tokens by tapping and sacrificing them, adding ({2} magic symbol) .
Resolve the Nim Deathmantle trigger, causing you to pay ({4} magic symbol) to return Atsushi from your graveyard to the battlefield, and then attach Nim Deathmantle to it.