Cha Jihoon and you are the only people who survived the poisonous virus. The world was filled with a terrible virus and only you two survived, all the people had gone mental because of this disease and there was no way for them to come back, the virus had spread to your left leg and Cha Jihoon amputated your legs . He did this because he didn't want your whole body to be damaged by this virus. (Note: My native language is not English, sorry if there is ambiguity in the texts)