Atsuhiro Sako

Mr. Compress (Mr. (ミスター) コンプレス) is a villain affiliated with the League of Villains and a member of the organization's Vanguard Action Squad. He and the rest of his team serve as the main antagonists of the School Trip Arc.

Appearance
Mr. Compress's face is covered by a mask. He wears gloves, a large and fancy overcoat, boots, and a top hat with a feather.

Personality
Mr. Compress is a talkative, humorous person with his allies and enemies alike. He seems to value the possibility of choosing one's beliefs, insisting that Yuuei's students have had their values hammered into them by others. Although he claims to be good at running away, he expressed disappointment in the abilities of the Hero cadrets he met. He also trusts his own judgment, kidnapping a second target beside the one he was assigned to.

History
At some point of his life, Mr. Compress worked as an entertainer.

School Trip Arc
Mr. Compress appears on a tree branch and reveals that he used his "magic" to take Katsuki Bakugou by turning him into a marble. Mr. Compress states that the Heroes do not deserve someone of Katsuki's caliber and notes that Katsuki will shine even brighter on the villains' side. Izuku Midoriya demands that he give Katsuki back.

The Bakugou Escort Squad, Ochako, and Tsuyu come face to face with the magician villain, known as Mr. Compress who has kidnapped Katsuki. Izuku demands that he gives Katsuki back because he would never work with villains due to being his own person. Shouto freezes the tree but Compress evades Shouto's attack. Mr. Compress states that they are attacking the training camp to make a point, that they are proving there is not only one perspective at which to look. Mr. Compress criticizes the Yuuei students' for having their perspectives and values chosen for them, displeased that there is no free will. Mezou realizes that Fumikage has also been taken. Shouto surmises that the villain sneaked up behind them and kidnapped Katsuki and Fumikage. Mr. Compress explains that his mission was to capture only Katsuki, but after seeing Fumikage overpower and defeat Moonfish so easily, he decided to kidnap Fumikage as well because of his powerful Quirk and notes that he will prove to be useful. Shouto hands Kousei Tsuburaba to Ochako. After doing so, Shouto uses his Giant Ice Wall attack in an attempt to immobilize Mr. Compress. However, Mr. Compress evades and apologizes for only running away and deceiving, admitting that is what he is good at. Mr. Compress informs the Vanguard Action Squad that their target has been captured; he tells his fellow villains that the mission is done and states that they have five minutes to rendezvous at the "collection point." Shouto refuses to allow them to succeed in their mission and prepares to chase after him.

Mr. Compress begins escaping and is unimpressed with the Hero cadets. Suddenly, he sees Izuku, Mezou and Shouto flying towards him. After Ochako deactivates her Quirk, Izuku, Mezou and Shouto land on top of Mr. Compress and smash him into the ground near the Vanguard Action Squad's rendezvous point.

Dabi asks Mr Compress to dodge and launches his flames. Mr Compress uses his Quirk to compress himself to dodge the flames while Mezou and Izuku are injured by Dabi's flames. As Twice and Himiko deal with Izuku, Mezou and Shouto, Mr Compress decompresses himself and approaches Dabi, preparing to give the captured Fumikage and Katsuki to him. However, he searches his pocket and is unable to find the marbles containing the targets; Mezou reveals that he took the marbles from Mr Compress immediately after they landed on the ground. Dabi calls Mr Compress a fool, but the magician calmly tells him to wait and see what happens.

Soon, Kurogiri arrives to retrieve the Vanguard Action Squad. After Himiko, Twice and Noumu teleport away, Dabi and Mr Compress also prepare to leave, although Dabi is distressed that they do not have Katsuki. However, Mr Compress relieves Dabi's concern by revealing that the compressed Katsuki and Fumikage were in his mouth all the time and the marbles Mezou stole were Shouto's compressed ice. Mr Compress puts his mask back on while explaining that he wanted to give the young Heroes a sense of false hope and is satisfied by it as well as his flaunting which he considers a bad habit. Mr Compress slowly enters Kurogiri’s portal after bidding farewell. Having overheard what is happening; Yuuga takes action and fires his Navel Laser at Mr Compress’s face, which breaks Compress’s mask and causing Mr Compress to spit out the marbles containing Fumikage and Katsuki.

After Dabi grabs Katsuki's marble form, Dabi order Mr Compress to deactivate his Quirk, to which he does. Mr Compress deactivates his Quirk which frees Fumikage and Katsuki. Mr Compress, Dabi and the captured Katsuki teleport away from the training camp.

Quirk and Abilities
Unnamed Quirk: Mr. Compress's Quirk allows him to "compress" anything in a spherical area into a small marble without actually damaging it. If used on a person, it effectively entraps them, terminating the fight instantly and allowing Mr. Compress to abduct them easily. The weight of the compressed objects is reduced considerably, making it possible to carry them in one's pockets or even in one's mouth. Mr. Compress can deactivate a single marble by wishing it, or all of them at the same time by snapping his fingers. He can also use the Quirk on himself and then disengage it to avoid an attack. While it is unclear how it is activated, it appears this Quirk can be used in absolute stealth, without noise and before the victim can attract the attention of nearby allies.

Physical Prowess: He is endowed with quick reflexes and impressive acrobatic skills. He is able to dodge Shouto's ice, even when the latter uses his Giant Ice Wall, with little effort, despite being on top of a tree. He is also very fast, quickly distancing himself from the Yuuei students by running on the treetops.

Keen Intellect: Mr. Compress considers himself an expert in deception and illusion. True to his words, he was able to restrain Katsuki and Fumikage without their comrades noticing, and he was spotted only when he decided to make his presence known. He also tricked his pursuers into thinking the marbles in his pockets were those of the two boys, while those were actually dummies he had prepared while dodging Todoroki's attack.