As with her brothers Toya and Natsuo, Endeavor neglected her in her childhood and didn't want to use her as his successor. Despite this, Fuyumi is the only child who is more able to look past their father's faults and forgive him for his previous behavior, especially since his father tries to atone his mistakes and be a better person.
Fuyumi is more than aware of how messed up her family turned out because of Endeavor's abuse, while expressing some fear of but she is the one who supports Enji the most in his effort to improve and fix his family issues. She is surprised to hear that he regularly visits her mother and listened to her voice his inner troubles. She was even horrified to watch the report of Hood defeating him but cheered on his persistence.
Her attempt at a family get-together following Endeavor's battle against Hood was what she expected to be a chance for Shoto and Natsuo to try to start a dialogue with their father, although it did not end too well due to Natsuo's animosity towards Enji. Fuyumi told Shoto she was quite hopeful and proactive with getting her father and siblings to mend relations with each other because of his recent progress.
She tries again months later with another family dinner, in which she also invites Izuku and Katsuki, although the outcome was not much better. Fuyumi confided in Shoto that she does have resentment to Endeavor but wants to move past it, for the future.
Although her initiatives have not yet been very successful, Enji thanks his daughter for all the support she has given him, thinking that Fuyumi doesn't know how much he has been saved by her.
When he leaves with the boys, he once more thanks Fuyumi for her actions who only responds to his gratitude with a smile. Endeavor later revealed that he is building a new house for the siblings and their mother, while he remains at their house alone.
Like her brothers Natsuo and Shoto, Fuyumi visits her mother for time to time in the hospital. The two appear to have a positive relationship.
Fuyumi cares so much for her mother physical condition, as it could be seen when she brought her a set of warmer clothes, but especially emotionally, reprimanding her brother Natsuo to mention her father in front of her, even though they had agreed not to.
In spite of the latter, she is surprised to learn that her father has visited Rei several times, although at the moment they have not seen each other face to face.
From the little that is known of her relationship with Toya, Fuyumi seemed to have a good relationship with him when they were kids, as they used to play together. Nowadays, Fuyumi mourns his death and she prays at his altar. Unlike Natsuo, she does not seem to blame their father for his death.
Fuyumi has a good relationship with her younger brother Natsuo, and as with Toya, they usually played together as kids. The pair still get along in their older years, with Fuyumi regularly teasing him in their visit to their mother, to his dismay.
However, unlike him, Fuyumi is able to look past their father's faults. She also wishes for him to see that she is trying so hard to fix the family that Endeavor broke, and that everyone can live together as a real and normal family. While Natsuo doesn't agree, for Fuyumi's sake, he is willing to begrudgingly participate in which his father is present, to respect the feelings of his sister, although this inevitably generates tension and Natsuo usually leaves to avoid more problems.
She also expressed concern for him after he was attacked by a villain, which he assured her.
When he arrived home late after the Kamino Incident, she berated him because of the danger going on and directed him to their raging father.
During the Pro Hero Arc, she spent time with him and their other brother Natsuo Todoroki before they watched as the latter told off their father for his previous treatment to him and his siblings. Fuyumi became upset, telling Shoto of her desire of being a real family, something he sympathized with. Fuyumi watched him expressed a similar desire of seeing the man Endeavor will be.
Fuyumi is aware of the difficulties that Shoto has in relating to other people, so he is glad to know that his brother has friends in the U.A. During the Endeavor Agency Arc, she decides to invite everyone to a dinner to meet them. After a dinner, she once again confided in him after the dinner was turbulent. Shoto was grateful to her for her intentions.
Eager to meet Shoto's friends, Fuyumi invite Izuku and Katsuki to dinner at Todoroki Abode with her family. At all times she is kind to them and both praise her cooking skills. However, dinner does not end as she would have liked due to the tension between her brother Natsuo and her father Enji. While talking with his brother Shoto about the matter, she is criticized by Bakugou to talk about their family drama in front of them for it was ruining the evening, to which she apologizes, while Izuku voices his thoughts on that Shoto is a very kind person waiting for the right moment to forgive his father.
After dinner, Fuyumi says goodbye to them and she thanks Izuku for being Shoto's friend.