Ren feels indebted to Eclair for stopping him when he was under the influence of the Curse Series, and is released into her custody soon after. He learns swordsmanship from her properly, becoming a far more defined "Sword Hero" as a result. Later on, when Eclair's sense of justice is challenged by reality and she starts to pick up Naofumi's bad habits, both of them start to worry about the dangerous path she's treading and the latter entrusts Ren to keep her morally in the right. Later on it is implied that his feelings for her are romantic in nature, and Naofumi, to some extent, supports him in this by leading her to go to his house for a christmass dinner, rather than staying up all night to thank santa due to her never having been told the truth that he doesn't exist.