[@KoL] Let's just put it as, he learns it and loses it when he gets another power, but if he sees a different better power he'll take it, like if he fights Crimson and takes her flash step, and fought someone else that had a cooler power ( in his case ) the he'd take it and lose the flash step because he's focusing on the new power. I guess you can say he's like a pokemon, he remembers certain moves but can't keep them all. 

I feel like Eiko and Crimson will be good friends