Setsuna Tokage/Synopsis

U.A. Sports Festival Arc
Setsuna finishes the Obstacle Race at 39th 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 Reiko Yanagi for the Cavalry Battle, and doesn't object once Itsuka suggests for their team to allow Team Tetsutetsu to participate in the 1 vs. 1 battles in their place.

Forest Training Camp Arc
Setsuna is seen with Yui Kodai, Kinoko, Pony Tsunotori and Reiko 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.

On the night of the third day, Class 1-B act as the scaring group during the test of courage exercise. However, that night the Vanguard Action Squad attacks. Setsuna and many of her classmates are knocked unconscious by Mustard's gas, being rescued later by Shota during the aftermath of the Vanguard Action Squad Invasion.

Shie Hassaikai Arc
Neito boasts to Class 1-A that all of Class 1-B have passed the Provisional Hero License Exam while in Class 1-A two students failed.

U.A. School Festival Arc
During the U.A. School Festival, setsuna participates in Class 1-B's original play, "Romeo, Juliet and the Prisoner of Azkaban: The Return of the Kings!".

Joint Training Arc
Setsuna, 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 fourth round of match-ups. As the fourth round begins, she tells her teammates that the first team to make a move will win. She leads an ambush against Katsuki and his teammates, being fully aware of Kyoka's Quirk and came up with a countermeasure by creating a lot of noise to trick them.

Setsuna then uses her Lizard Tail Splitter Quirk and splits herself into many pieces to attack Katsuki and the rest of the Class 1-A team. She also orders Kojiro Bondo and Togaru Kamakiri to trap the other 1-A opponents while distracting Katsuki. They struggle to fight back because her pieces are too small to target. She then tells her team to take out Kyoka first as she is the most troublesome.

However, Katsuki manages to protect his teammates by blasting Togaru straight in the face. This prompts Setsuna to tell her team to retreat in hopes of initiating a new strategy to ambush 1-A again. Upon realizing that 1-B is underestimating his team's strength, an enraged Katsuki commands his team to charge forward. Setsuna observes Katsuki's newfound demeanor, wondering how he managed to cooperate well with his teammates despite most likely working alone.

She then attempts to ambush Katsuki once again with a combined attack with Kojiro. However, this fails as the explosive hero easily takes out Kojiro with ease. Setsuna tries to retrieve some of her dismembered parts, only to find a grenade attached to one of the parts. This creates a loud explosion from a not-so-far distance. Setsuna manages to evade the attack and believes she successfully escaped 1-A's grasp. Unfortunately, Katsuki blasts his way towards Setsuna and emits a Point-Blank Stun Grenade straight at her body. Setsuna exclaims that Katsuki changed too much as she gets engulfed in the attack.

Afterward, Setsuna and her classmates lose the match due to their plan lacking the flexibility similar to Juzo Honenuki in his match, as mentioned by Vlad King. A sullen Setsuna apologizes to her team for failing to impress their class, but her teammates immediately shrug it off, deciding to take the hard loss as a good learning experience. She also apologizes to Neito for ruining their class' chance of beating Class 1-A, in which Neito tells her it's alright and that those who make mistakes always grow stronger from the outcome.

After her defeat, Setsuna stays to watch the last round along with the rest of the students. The Joint Training Battle ends with victory for class 1-A. Despite the fierce competition and the result, the exercise ends on good terms between both classes, and later Class 1-B visits Class 1-A's dormitories for socializing and dinner.

Endeavor Agency Arc
With the start of the second Hero Works-Studies, Setsuna and Momo intern under the Pro Hero Majestic during U.A. High School's winter break.

My Hero Academia: World Heroes' Mission
During the Work-Studies, the Majestic Agency is invited by the World Heroes Association to participate in an operation against Humarise, an anti-Quirk cult that had recently carried out a Trigger Bomb terrorist attack, causing the deaths of thousands of people.

As a member of the Majestic Agency, Setsuna travels to Singapore to raid Humarise's branch there. Although the mission ends successfully, the results are not satisfactory, as no clues are found as to the whereabouts of the Trigger bombs or their leader, Flect Turn. Because of this they must remain in the city investigating.

Days later, Flect Turn announces that they have placed Trigger Bombs in various countries, including Singapore, and that they will explode in two hours. The entire Singapore Task Force immediately begins to search for the bombs. Momo uses her Quirk to create sensors to look for the Trigger Bombs, and Setsuna uses her Lizard Tail Splitter to distribute them among the other heroes. They eventually manage to find the weapons, but must confront Humarise's agents stationed there to protect them.

Fortunately, thanks to the actions of Izuku and his teammates, the bombs do not explode. After this, the heroes defeat and imprison the last remnants of Humarise. Big Red Dot, Singapore main hero, personally thanks the Majestic Agency for their help. Once the crisis is over, Setsuna leaves the country with her team and returns to U.A. High School.

Paranormal Liberation War Arc
The months go by until it's late March. Thanks to the police investigation and its spy Hawks, the Hero Public Safety Commission has found out the plans of the Paranormal Liberation Front and its allies. With this information the Commission organized a large force of Pro Heroes, divided in several teams to take down the villain organization.

While a team of heroes raid the Jaku General Hospital, where the Nomu are created, another team does the same at Gunga Mountain Villa, the Front's main headquarters. Setsuna is a member of the Villa Backup Team along with some of her classmates and Class 1-A students. Their mission is to provide support to the heroes who raid the Gunga Mountain Villa and prevent villains from escaping.

After the raid commenced, heroes gained the upper hand, taking down many of the Front's members. However, the Jaku team couldn't stop Tomura Shigaraki from waking up and ordering Gigantomachia to come to him with the League's members. This results in the giant defeating many heroes as he simply walked towards Jaku City. Midnight tries to stop him, but is defeated and she radios Momo to notify her of the situation and give her the key to stop Gigantomachia. Momo then rallies the other students to prepare for an attack against the enemy.

Following Momo's lead, the U.A. Students prepare a trap for Gigantomachia. Juzo Honenuki uses his Quirk to soften up the ground as part of Setsuna appears behind him telling him to get back because Gigantomachia is close enough now. Juzo asks her if Neito's group is safe, but she tells him they can't focus on them now, even though she is worried about them too.

Momo gives each student a 30-liter vial filled with sedative that she created with her Quirk. The plan is that, when Gigantomachia falls into the trap, at least one of them must chuck their vial into his mouth, so the giant villain will fall asleep. As they set up a trap, they are informed that the members of the League of Villains are riding on Gigantomachia's back.

As they planned, Gigantomachia falls into the softened ground and the students begin their assault. While some of them attack the League of Villains' members that are riding on his back, others try to force Gigantomachia to open his mouth and throw the sedative into it, but Gigantomachia easily blows them all away with one breath. The situation is worsened when Dabi uses his flames to set the area on fire, preventing the students from advancing towards them.

Despite this, Eijiro Kirishima manages to break through the wall of fire and climbs his way up Gigantomachia, where he manages to chuck a canister into his mouth. Seeing him, Gigantomachia is about to smash Eijiro with a slap, but the students start firing at him with cannons created by Momo, while Setsuna flies in and manages to grabs Eijiro out.

Several heroes led by Majestic arrive to take charge of Gigantomachia now that he has ingested the sedative, because the more he moves the faster it will spread. Gigantomachia, however, takes on an armored appearance and easily defeats heroes, and continue on his way to Tomura. Before being defeated, Majestic uses his Quirk to bring all the U.A. students to safety, who can only watch helplessly as the giant devastates everything in his path.