Tomizo Todayama is the second oldest Oni of the core three at twenty-eight, he is still very much a novice. He still acts like a novice with many Oni matters and enjoys the simple things that life has to offer him. He is also one of the more clumsy people, this trait often leads to problems both in and out of battle. A green Oni, both in color and appearance, he is still learning how the world around him works. Having only just become an independent Oni during his introduction, he sticks close to Hibiki and Ibuki and looks to them for guidance. Eager to do please his master but do things in his own style, he often meets conflicting points of views from others, but continues on with what he believes is "his" way. His basic green form and the easiest form for him to reach. To become this form, Todoroki simply needs to pluck his brace strings, the vibrations from the strings cause his body to be hit by massive lightning bolts, changing him into his Oni form. Todokori also gains a second "oni face" which is a crest that forms on his forehead. He was first seen in episode fourteen greeting Asumu at a hospital. He later returned with his master, Zanki, to fend off a pair of Makamou. Originally he was to be the next Zanki, but declined the offer from his master so that he could create his own legacy as Todoroki. Even though often misguided, Todoroki will stand by his friends no matter what comes their way.

When he became a solo Oni, Zanki had some trouble accepting the way that he fought the Oni and his "cleansing" of the battlefield. Eventually Zanki came to accept that this was Todoroki's way of being an Oni. Todoroki saw Hibiki as a teacher, and Hibiki offered Todoroki guidance on being a solo Oni and the new challenges that life would bring him now that he had no master. Todoroki soon came to find fighting the Oni on his own to be a tough challenge. In response to this, Zanki returned to be his supporter and offer advice whenever he could. Todoroki had a crush on Hinaka Tachibana. One day he gathers enough courage to asks her out on a date on her birthday. The date goes horribly wrong for Todoroki, he makes a fool of himself and ruins her gift. Hinaka became upset with Todoroki and the two were distant with each other for a while. Late in the series after the Shuki incident, Todoroki was literally stepped on by a giant Makamou. This left the others questioning whether or not Todoroki would ever be able to henshin again. Zanki feared this would cause Todoroki to go into a state of depression, indeed it does. Zanki believes that Todoroki was born to be an Oni and that he knows no other way of life.

Eventually Zanki meets his end, but puts a spell on his soul to allow him to remain on earth until Todoroki no longer needs him. It was around this time that Hinaka and Todoroki became friends again, even though she offered her help to teach him how to walk again, Todoroki declined. Even when Zanki helped him out, Todoroki said he wanted to do it on his own, otherwise he would never be able to show that he is an independent warrior. Todoroki learns to walk again and rushes into Zanki's final battle, the both make quick work of a large number of Makamou and soon it is time for Zanki to pass on. Todoroki and Zanki have one final cleansing session as Todoroki pays his final respects to his former master. After these events, Todoroki has finally become the man that he always wanted to be. He went from a new Oni, still worried about his skills and unsure about his ability to live in the world on his own to a confident man who works well with others and trusts in his own strength.