After Mob's involvement in a horrible accident, he has fallen into his highly destructive and ominous "???" state. Steadily advancing with Tsubomi's bouquet of flowers in hand, Mob wreaks incredible destruction across the city, and despite having grown a lot as an esper, Mob's friend Teru finds himself completely unable to put a stop to the destruction. Seasoning City is thrown into disarray, and upon feeling a similar sensation, Ritsu heads out into the chaos to help set his older brother straight once more.
The eleventh episode of Mob Psycho 100 III is an absolute whirlwind as several powerful espers attempt to subdue the rampaging Shigeo. The hopes of Seasoning City are all seemingly pinned on the former leader of the Claw terrorist group, Toichirō Suzuki.
Mob Drain
Arriving just in time to save his former subordinates, Suzuki engages Mob in the midst of the destruction and soon sees the extent of Mob's power that state. His son, Shō Suzuki, appears on the scene and saves his dad from a pretty sticky situation. In order to level the playing field slightly, Suzuki takes an energy attack from Mob head-on, absorbing some of his energy and using it to charge himself up in preparation for the incoming battle.
He asks Shō for help in executing a plan based on a very simple premise: Mob's current rate of energy release is guaranteed to lead him to run out of stamina, making it a matter of keeping him busy long enough for him to tire himself out. They engage Mob, going all-out from the very beginning of the battle out of an understanding of the severity of the situation at hand. Their best doesn't seem to faze the berserker in the slightest, and the older Suzuki takes on ample amounts of damage as the battle wages on. They soon realize how futile the battle is, and Shō even suggests that they retreat; however, Toichirō is unable to run away due to the wounds he sustained over the course of the short bout.
Just as Mob begins to charge the final energy attack to finish off his opponents, he lets out a stifled croak and briefly stops his attack. Internally, Mob is at war with himself, and trying to win against "the thing". The interruption gives Toichirō enough time to come up with an insane plan, and for it to work, Shō will have to vacate the area. The only way to stop Mob is for Toichirō to become a vessel for all of Mob's incredible power, the same way Mob did for him in the conclusion of their fight at the end of Mob Psycho 100 II.
He soon loses his nerve, and decides to escape together with his son. On their way away from the destruction, the Suzukis talk about the terrifying potential of psychic powers. The younger even goes as far as to say that he'll no longer use his powers in favour of living a normal life, something that is extremely difficult, but something Mob used to do nonetheless. When Shō asks his father what will become of Mob, the older Suzuki simply answers that no one will be able to stop him. The shot pans to an unconscious Teru, and further out to reveal Ritsu standing at the rooftop of a ruined building looking out at the destruction surrounding them.
Long Time No See
The Body Improvement Club locate Mob somewhere in the city and try to get him to snap out of his berserk state to no avail. He attacks them indiscriminately, and makes quick work of each of them. The level of force he uses against them is excessive, and it appears that Mob has severely injured some of his non-esper friends, but Ritsu arrives just in time, using his own esper powers to save them.
With bitter memories bubbling to the surface amidst the nostalgia of the brother who used to express himself; the brother he lost, Ritsu says that he'd lived in fear of the next time his older brother would become this "thing"; the alternate version of Mob that emerged on that one horrible day in their childhood. Ritsu tells Mob that despite the fear he feels towards him when he is like that, he understands that this is just another part of Mob; one that he accepts.
Internally, this exchange causes Mob to stir, and he rejects the notion that this immensely destructive force could also be a part of who he is, and he tries to beg Ritsu to stay away from him; but his little brother advances.
Ritsu tells his brother to stop going through tough times by himself, and recalls how Mob went as far as to try to keep his powers and emotions sealed away in an attempt to protect his younger brother. His percentage continues to increase throughout the duration of the exchange, and Mob ends up being unable to subdue the berserker any longer, It sends whip-like projectiles that entangle Ritsu and keep him fixed in place. Both he and Mob are helpless as the berserker advances towards Ritsu.
100%
In a moment of brilliance, Ritsu finds a conclusion: he will continue to be the little brother that Mob can open up to and one that Mob can expect to lend an ear to him whenever he needs it. The decision momentarily grants Ritsu an incredible burst of psychic ability as he is coated in an aura just like the one that is normally associated with Mob and his abilities. In this state, Ritsu is able to block an attack from the berserk state Mob and stand against him; however, the moment of epic brotherly intervention was short-lived as in the next few moments, Ritsu is totally defeated.
Sayonara Mob
Rushing towards the scene are the last individuals left in Seasoning City who are capable of making some kind of difference and snapping Mob out of this situation, Serizawa and Reigen. Throughout the latter stages of Mob Psycho 100 III episode 11, Mob struggles immensely with his sense of self in the form of an internal dialogue with a self and equally "Mob" not-self. They struggle to determine which of them is the "real" Shigeo Kageyama and which of them is "Mob", the false construction of a personality that resides within Shigeo Kageyama, and as the not-self continues to convince the other, more "complete" self of its incompleteness, it literally steals pieces from the more complete self. "Mob" has a goal – to break Shigeo and make him disappear so that he can do as he pleases, ending his soliloquy with a chilling statement: "The next time you wake up, I will be me."