Twelve sees Nine like a big brother. Sometimes he acts childishly, but when he is with Nine he acts more seriously. They both have a very deep connection with each other and they are like a family.
Twelve at first seems to see Lisa as a play thing for a while, with Nine constantly reminding him to not get attached to her. However it becomes clear that he begins to develop a strong amount of feelings for her, this shown when she runs away from her house and he chooses to find her and bring her to the hideout in which him and Nine are. He is very empathetic towards her and cares for her deeply as when she was trapped in the airplane with a bomb that Five had set up he was set on saving her, even with Nine's initial disagreement with such. After that Lisa runs away, thinking she is simply a burden in which he immediately goes off to find her as Five sends Sphinx a message on how she is held captive in the ferris wheel. All the while trying to disarm the various bombs attached to her body he comforts Lisa, telling her nothing is her fault, even when he betrays Nine on the atomic bomb's location as to save both Lisa and himself. After, the two go to an amusement park together Lisa is worried about Nine in which Twelve then sets off to save him, however later is found by Lisa who takes care of him as he falls unconscious, then later hugs him whilst crying when he regains consciousness, glad to see he is alive. The two together watch the sky as the atomic bomb will go off at any given moment, Twelve sharing on how he and Nine have always been alone and thought they needed nobody, however he was glad he had met Lisa, making her smile and cry as they reach out to hold each others hands when the atomic bomb detonates in the stratosphere. It seems they care deeply to each other, even to the point of possible romantic feelings.