Is up to you guys.
1 - Chikao Yuki - The second backstory for Kaisu/Chikao/Kizuna. Normal story, Chikao was studying at uni/college while his siblings/in-law did their thing. Got moved out and had his name changed. However, Kaisu's Jap-American, but that can be changed. Both parents had foreign names in the file, so... It'll require mild editing.
2 - Kizuna Jinrai - Sound familiar? Kyousuke had married another Rescue worker and she had gotten pregnant when she was transferred to the American branch of something UFDA. During an Extreme Disaster he lost contact with her once she had moved to America. He eventually forgot about her, because he's that kind of a guy. Meanwhile, Kizuna's mother was friends with the Yuki family and when she died they took in the baby Kizuna and raised him. His dyed blonde hair is a resemblance(not really XD) to his father. He naturally had a red-brown mix. When the mafia/gang/whatev. attacked their house at 34 Investigations(Kizuna had been in his last year at High School or something) Kizuna had to kill and almost died. After that trauma he had memory loss and forgot several things. Kizuna became another memory of his, another person. He had mild plastic surgery to fix him up after the attack and he later started training for the UFDA. Will require a few large drops of mild editing.
So, which one do you guys like better?