So basically these two are Marb's ADOPTIVE daughters that are octolings, but these Octolings CAN FUSE, with a device that i would like to show.
So more about them Yuko is younger than Eiko being the Fun laid back one that talks to her dad sometimes when she is not supposed too in an argument, disrespect strangers and is a bit of a prankster and troublemaker.
Meanwhile Eiko is the older one being the Calm, smart and Mature of two, even tho she love her sister, she does try to stop her from doing stupidities and by warning just giving her one warning if that's not very very serious.
When they fuse together, they turn into Yeïko (Yay-ko), that makes them more powerful in combat situations and makes them look a bit taller, Yeiko is not technically Eiko and Yuko, even if they fused, Yeiko is a whole different being, She is cocky, Doesn't fear anything and love destroying bad guys.
