Yokohama Disturbance IV is the twenty-second episode of the Mahouka Koukou no Rettousei anime.
Lu Gonghu's attempt to remove Hirakawa Chiaki is thwarted by Watanabe and Naotsugu Chiba. Mr. Zhou visits Chiaki and appears to cast a memory alteration magic so that she will forget about his involvement with her. Saegusa, Watanabe, and Tatsuya go to the detention facility and elicit a confession from Sekimoto on his intention (and unsuccessful attempt) to steal the Magic Thesis project data and locate the relic. Lu Gonghu appears again, apparently to silence Sekimoto, but is defeated by the three and taken into custody. Later, Tatsuya relays the information to Fujibayashi.
Tatsuya and Miyuki are visiting Kokonoe Yakumo at his temple when he tells them he’s heard they have something interesting in their possession and advises them to return it as soon as possible. Tatsuya replies he wasn’t aware it was been targeted. Yakumo also warns them to take care not to lose their bearings when facing the enemy. Miyuki is unsure what he means, but Yakumo tells them any further questions will come at a price.
The Shiba siblings are riding double on Tatsuya’s motorcycle when Tatsuya realises that they are being followed. He tells Miyuki, explaining it’s a crow familiar. Tatsuya says he wants to avoid revealing his powers and tells Miyuki to hang on, before speeding up.
The Shiba siblings arrive at FLT to find the lab in turmoil as Ushiyama directs the lab to repel a cyberattack. Tatsuya asks Ushiyama what’s going on and Ushiyama confirms it’s an attack but is confused as they don’t seem to have a specific target despite it’s large scale. The attack suddenly stops and Ushiyama tells them to stay on alert. He then asks Tatsuya what he wants, and Tatsuya tells Ushiyama he’d like to store something at the lab. The crow then lands on the roof and Tatsuya destroys it.
At their hideout, the destruction of the crow is reported to Chen Xiangshan but he doesn’t care as they know Tatsuya took the Relic to FLT. Another man reports FLT are counterattacking and Chen orders them to cut the lines. Chen remarks that the attack should have shaken Tatsuya’s faith in the labs security so it’s unlikely he will leave the Relic there. Lu Ganghu agrees that logically speaking that is true, though if he does leave it there then they just need to find a way to get the data from there. Chen then orders Lu to get rid of Hirakawa Chiaki before Zhou Gongjin has chance to visit her today.
On the twenty-third, Tatsuya is on a call with Hirakawa Koharu about her sister’s actions. Tatsuya tells her Chiaki’s actions will be swept under the rung and comments that hacking is a crime. Miyuki enters the room as the call ends and asks what it the call was about and Tatsuya explains Koharu sent her sisters telephone logs. Tatsuya then makes a call.
The Shiba siblings are at First High when it begins to rain heavily. Miyuki comments they can’t work outside in this and asks what Tatsuya’s plans are and he tells her that he’ll be debugging in the Robot Research Club today and he’ll come pick her up once he’s done.
Tatsuya arrives at the Robot Research Club and is greeted by Pixie. He suspends her functions and gets to work. After a while Tatsuya feels drowsy and tries to get up but when he gets dizzy, Tatsuya realises something is wrong and that the room has been gassed. Pixie comes over with a gas mask and to inform him of the issue. Tatsuya tells her to force vent the room and advises her he doesn’t need the mask. He then orders her onto standby and to record what happens in the room.
A short time later someone enters the room. The man checks that Tatsuya is asleep then proceeds to plug a device into the console Tatsuya was working on. The light is suddenly turned on and the man, revealed to be Sekimoto Isao turns around to see Chiyoda Kanon. Kanon accuses Sekimoto of being an industrial-academic spy and Sekimoto retorts he was just making a backup. Kanon states that’s unlikely and asks Tatsuya for confirmation. Sekimoto is shocked to see Tatsuya is awake and blurts out that the gas didn’t work. Kanon demands Sekimoto surrender, but he tries to resist and Kanon has to incapacitate him with magic.
At the Magic University Affiliated Tachikawa Hospital, Mari is on her way to visit Chiaki with Chiba Naotsugu. In the reception, Mari apologised for making Naotsugu come with her when he’s shipping out the next day, but Nao tells her not to mind as he wanted to be with her. Meanwhile Zhou takes the elevator to Chiaki’s floor and sees Lu Ganghu looking for her room. Zhou immediately presses the alarm. In reception, Mari and Naotsugu hear the alarm and upon realising it’s originating on Chiaki’s floor, Mari and Naotsugu immediately rush up the stairs with magic. Lu Ganghu tries to break into Chiaki’s room, but Naotsugu reached the landing before he can. Naotsugu and Lu Ganghu immediately recognise each other and ready for combat. Lu charges first and an intense melee ensues. Neither can harm their opponent but Naotsugu is pushed back until he reaches the wall. Lu makes an attack and Naotsugu is forced to block it while taking an injury to his arm while counterattacking with his CAD blade and injuring Lu’s side. Mari finally arrives and casts a spell at Lu, but he blocks it and then jumps, using the lights to reach the floor and escapes. Mari checks Naotsugu is ok, and he tells her that Lu Ganghu is from the [Great Asian Union|Great Asian Union’s]] special forces.
At home, Tatsuya calls Fujibayashi Kyouko and reports the incident at the school with Sekimoto. Tatsuya sends her the recording that Pixie made of the incident and Fujibayashi infers Tatsuya would like the matter settled soon and informs him that Kazama Harunobu has ordered the same. The call over, Kyouko lets Chiba Toshikazu back into the car, apologising as the call was confidential. Toshikazu asks what intel the informant gave her, and she indirectly tells him it was a video of a collaborator with a hacking tool. She then tells him she’s starting the hunt and would like his help.
At their base, Chen informs Lu of Sekimoto’s capture and orders him to prioritise silencing him over Chiaki.
Tatsuya visits the Public Morals Committee’s headquarters to ask for permission to see Sekimoto, but Kanon refuses. Tatsuya asks for an explanation as the decision lies with the school and he’s not happy to be told no without a reason. Kanon snaps and tells Tatsuya straight that trouble loves him and she doesn’t want more work when she’s swamped. Mari steps in and says it wouldn’t be an issue if he went with her and Mayumi, since they are going anyway. Tatsuya agrees.
Chiaki is alone in her hospital room when she is visited by Zhou. Zhou asks how she is and Chiaki asks how he got in, but Zhou simply says he used a special move. Chiaki starts to apologise for failing when Zhou helped her but is put into a daze by the scent from Zhou’s flowers. Zhou then tells her to forget all about him if she has regrets and she does.
Mari, Mayumi and Tatsuya visit the Hachijouji Special Detention Centre to see Sekimoto. They ask about the Thesis Competition and Tatsuya informs them his share of the work is completed. Mayumi and Tatsuya go into the observation room while Mari enters Sekimoto’s room alone. Sekimoto is surprised to see her but is confident she can’t use magic, but she does, and he’s put under a trance. Watching on, Tatsuya recognises it as scent-based mind control. Sekimoto explains after he took the research data, he was supposed to search Tatsuya for the Relic. Mayumi is surprised and asks if he has one, but the alarm goes off before he can answer.
The three exit the rooms and as they check the alarm, Tatsuya sees Lu Ganghu approaching. Tatsuya comments it’s too late to flee but Mari stops him taking point, having him hold back to defend Mayumi. Mari readies her stance and pulls out her weapon. In response Lu charges at her. Mayumi uses magic to offer fire support while Mari engages at close range and the flurry of attacks pushes him back. Lu changes stance and charges again, but this time dodges Mari and charges at Mayumi instead. Tatsuya uses Gram Demolition to stop Lu’s charge and disable his magic and reopening his wound from the fight with Naotsugu. Mayumi resumes her attack and stops him advancing again. Mari then closes in from behind and readies a combination attack and ignites powder in Lu’s face. She then swings her sword and when Lu dodges it, the other two floating blades pierce his shoulders and take Lu down.
At home, Tatsuya receives a report from Kyouko, telling him the spies were captured with the exception of Chen, who escaped. Tatsuya asks where the intel about the Relic was leaked and Kyouko reports it was the militaries accounting data that was leaked. Kyouko wishes him luck for the competition and ends the call.
Everything resolved, Tatsuya finally takes a moment to relax. Miyuki comes in and notices. She comes over to check him but when she gets close she starts to lose control. Tatsuya suddenly comes to and it makes Miyuki jump, causing her to slip and they nearly kiss by accident, though Tatsuya catches her in time. They sate at each other for a moment and then Miyuki gets flustered and flees the room in embarrassment. In her room Miyuki thinks at what she nearly did. Tatsuya arrives and asks to come in. She opens the door but starts crying. Seeing this Tatsuya things it’s because he worried her and so apologises and assures her he’s fine and tells her to call it a night.