Marlena, a dark elf, is a pivotal rebel ally to protagonist Takeru during their failed uprising against the demon lord Lucifon. Following Takeru's extended imprisonment, she visits him bearing a high-stakes mission: to propel him twenty years into the past. Her objective is for Takeru to rewrite history by persuading her past self to dedicate fully to the rebel cause against Lucifon.

In this past timeline, Marlena fights alongside the rebel forces. Her younger self encounters the time-displaced Takeru, now using the alias Eto. Eto strives to convince her to embrace a decisive role in the conflict, leveraging her knowledge and abilities to fortify the rebellion. Her involvement proves instrumental in rallying allies and formulating strategy against Lucifon's forces.

Her actions uniquely bridge both timelines: she initiates the plan to correct the rebellion's failure while also actively participating in the altered historical events. Her identity as a dark elf and steadfast loyalty to the rebel cause remain defining traits throughout her appearances.