Yakumo's growing friendship with Harima leads him to trust her with the critiquing of his manga drafts and keeping his pastime a secret. Later on, she takes on the task of assisting him on the actual inking of pages, which causes them to spend many hours together alone. Yakumo eventually develops deeper feelings for Harima than just the master-apprentice relationship. However, she keeps them hidden from him as she realizes he is in love with her sister. She initially decided to give in and support his relationship with her sister, as she regards Tenma as the most important person for her in the world and wants to make her happy. However, once her feelings for Harima became too strong for her to contain, she anxiously declared her affection for him, only for Harima to misinterpret it as her love for Harima.