Mariko's father is named Kurama. I just think of Yu Yu Hakusho to remember.
Well, the cell phone isn't necessarily Mariko's weakness, you know. A bomb was implanted in her, so it's not an inborn weakness, unlike her recognizing Kurama. But I hated when Kurama abandoned Nana like that for Mariko. But, I was sad when both Mariko and Kurama were blown half way to hell. Then Lucy kills the dude with the cell phone before he kills Nana.
If Lucy got the phone? I don't think she knew the significance behind it. She would probably just break the phone, which would doom Mariko. But what if the cell phone was destroyed? Maybe that would negate the bomb (I don't remember if they said anything about that. Hm, loophole!
). And yes, Lucy got seriously beat up.