Ken couldn't stop himself from saving Jane when he heard the latter showing faith in him. He felt like he was acting the same as Sol, becoming what he hated, which prompt him to act and help her.
'I've made a mistake; I should've let her die. I should let them both die to remain safe from their possible betrayal in the future.'
Ken thought to himself while running by Jane's side. He could leave her behind and outrun her easily, but he was semi-hoping that Diana will die before he gets there, freeing him from guilt over her death. His conscience was filled with guilt over his thoughts when he thought of the girls' sincerity while dealing with him.