Reiko finishes the Obstacle Race at 26th place. It is later revealed by Neito that she was a part of the group of Class 1-B students who went along with his plan to hold back in the Obstacle Race so that they could observe Class 1-A's Quirks and tendencies. She teams up with Itsuka Kendo, Kinoko Komori, and Setsuna Tokage for the Cavalry Battle. Team Kendo attempts to snatch Team Midoriya's headband like many other competitors but Team Todoroki ends up freezing multiple rival teams, including her's. Shoto Todoroki proceeds to snatch Itsuka and Rin's headbands. When the event ends, Reiko and her teammates don't object once Itsuka suggests for their team to allow Team Tetsutetsu to participate in the 1 vs. 1 battles in their place.
Reiko is seen with Yui Kodai, Kinoko, Pony Tsunotori and Setsuna when Classes A and B are heading out for the school trip. On the second day of the training camp, she listens along with the rest of her class as their homeroom teacher explains that they will be training their Quirks. During the aftermath of the Vanguard Action Squad Invasion, Reiko is one of the eleven students who received injuries of varying degree along with being one of two we were not shown being injured, the other was Nirengeki Shoda.
Like the rest of her classmates, Reiko participates in the School Festival by helping her friend Itsuka prepare for U.A.'s Beauty Pageant contest. When Neito Monoma, Tetsutetsu Tetsutetsu, and Yosetsu Awase barge in to check on Itsuka, Reiko tells them not to barge in so unexpectedly. Later on, Reiko presumably watches Itsuka perform in the Beauty Pageant during the School Festival.
Reiko, along with the rest of Class 1-B are pitted against Class 1-A as part of the Joint Training Battle. She is placed in the fifth round of match-ups. As the matches go on, Reiko and her teammates watch Neito in exasperation as he shows further signs of insanity. While waiting for their upcoming match, Reiko notes that Izuku Midoriya could serve as a major threat to Team 5-B's victory, highlighting his newly-developed fighting technique. She then notes that Izuku could easily catch her team off-guard even by a second.
When their respective match starts, Class 1-B proceeds to initiate their plan of taking down Izuku Midoriya as top priority. As Ochaco Uraraka and Minoru Mineta attempt to catch their enemies off-guard, Reiko and her teammates (excluding Neito) use this opportunity to attack them with a combined attack. Reiko begins the attack by sending multiple metal objects towards Class 1-A with her Quirk. As Mina defends her team with her "Acid Veil" Super Move, Minoru notes that Reiko is aiming the objects at random targets as they don't seem to be homing in on their team. Upon scattering 1-A, Team 1-B vows to track down the remaining members in hopes of capturing them for a chance at victory.
However, 1-B's plan is interrupted when Deku's One For All Quirk begins to unleash black tendrils that send him flying across the battlefield. Reiko and her teammates notice Izuku destroying multiple sections of the battlefield. After Hitoshi and Ochaco manage to stop Izuku's out-of-control Quirk, Neito tries to ambush the two 1-A combatants. Neito's attempt fails, which leads to Reiko saving him from getting beaten down by Ochaco. The rest of her teammates follow up, allowing Mina and Minoru to navigate their location. With all participants together, the final match becomes an all-out brawl between 1-A and 1-B.