Psychic Sisters Arc

The Psychic Sisters Arc is the sixteenth arc of the series.

Plot
Three A-Class heroes, Forte, Butterfly DX, and Chain'n'toad go on to give their new neighbor a visit to introduce themselves, but end up being intimidated after King faces them. King wonders where Saitama went.

Two days after the battle with the Monster Association, Saitama is promoted to A-Class Rank 39, but his home was destroyed as a result of his previous battle and he has to move to the newly established Apartment Complex, built by Metal Knight with a Defense System, assuring safety. Black Sperm and Overgrown Rover, the sole survivors of the previous battle, keep on bothering Saitama and offer their service in exchange for letting them in. Seeing that Saitama hasn’t discovered that they're monsters, they decide to follow where he is going without knowing that it will be in the Hero Association HQ.

However, as soon as Saitama enters with the two and they are detected as monsters, the Defense System automatically activates and starts to attack the two. Thinking that he was the target, Saitama easily destroys the defense robots up to level 10. Questioned by the security about the robots, Saitama explains that they just blew up and was also covered by King, who came to visit.

At the same time, Sweet Mask, now with black hair, has completely changed into a different person and has developed an obsession in regards to Saitama. He takes down the newly-formed boy group known as the "Soda Pop Boys", who had provoked and challenged him while questioning his capabilities as a hero and an idol. It seems that he gained a new power in the aftermath of the war against the Monster Association.

Back at the newly-built complex, Metal Knight takes the footage and discovers that Saitama was the culprit, and quickly takes interest in him. While he finds Saitama’s background as normal, he concludes that his strength is on par or even greater than an S-Class Hero. He decides to keep an eye on him for now. Introducing himself to his new A-Class neighbors, Saitama gets into a fight with Forte, Rank 31, after unintentionally offending him and they make a bet on whoever loses will take care of Black Sperm and Overgrown Rover. But before they could begin, Forte is bumped by Fubuki’s car, who then demands Saitama to come with her. Saitama gives Black Sperm and Overgrown Rover to Butterfly DX since Forte technically lost the fight since he was knocked out. Fubuki's actual purpose is to interrogate Psykos, the imprisoned leader of the Monster Association about her “Third Eye” ability and what she had seen through it. However, Tatsumaki has already started making her way to finish Psykos, easily tossing the Blizzard Group. Fubuki and Saitama take Psykos with them but Tatsumaki eventually catches up. Fubuki tries to stop her but Tatsumaki is simply stronger.

Saitama interrupts their fight, and challenges Tatsumaki. The two destroy parts of the Hero Association HQ, and fight in the area around the HQ, with the two continually trading barbs at each other. Tatsumaki's telekinesis pushes Saitama into another city far from the Hero Association HQ. As they clash, their fight gets carried away, leading them to dispose of a villainous gang in N-City, a Dragon-level monster in H-City that Metal Bat had been dispatched to kill, as well as Sonic, who was chasing after them intent on fighting Saitama. Eventually, Tatsumaki tired to the point of reopening her old wounds, forcing her to end their battle by dropping Saitama into a crevasse she created on the spot, before sealing it up again. Back at Hero's Association HQ, Fubuki disbands the Blizzard Group, claiming them to be too weak, before flying off to confront her sister.

Fubuki then meets with her sister Tatsumaki on the open field outside of A-City. Tatsumaki detects Fubuki's determination to defeat her, but reiterates that Fubuki is still very weak, emphasizing the need to get stronger to survive as no one will protect her. With the intention to attack, Fubuki mentions that she wants to defeat Tatsumaki for her own sake. Before Fubuki initiates the attack however, the members of the Blizzard Group rush to the scene to help Fubuki fight, with the intention of paying back the kindness Fubuki has given them. The group promises to get stronger and pleads Fubuki to stay with them. Tatsumaki then cuts them off and threatens Fubuki that she will not hold back now that Fubuki has given her final farewells. Fubuki hesitates, with Tatsumaki detecting it as a weakness caused by the Blizzard group and proceeds to attack. Tatsumaki telekinetically throws a boulder, which Mountain Ape catches. The group prepares for battle by demonstrating their respective psychic abilities. Tatsumaki readies for an attack, however she reopens her wounds again and fall to her knees, the reason being Saitama's emergence from the crevice. Saitama had closed the gap between himself and Tatsumaki while he was under the ground, and he emerges in between Tatsumaki and Fubuki. Fubuki tries to tell everyone to stop, as Tatsumaki's wounds are still fresh, and she may die because of it. Saitama then adds that this could be their chance to defeat Tatsumaki while she is weak. However, the Group refuses, realizing that defeating Tatsumaki will not make them stronger, and the need to grow stronger together. Tatsumaki leaves them on this conclusion. Fubuki remembers their original objective to secure Psykos, but Saitama disappears before Fubuki can say anything to him. Tatsumaki flies towards the direction of the City- A Hero HQ. As she lands, Saitama appears behind her. Tatsumaki gets angry at Saitama, calling him a baldy with no friends. Saitama then asks her why she became a hero if she's trying to cut relationships with people. Tatsumaki replies with "Bla-", actually referring to Blast.

A flashback is shown dating back 18 years before the series, and 15 years before the creation of the Hero Association. A young 10-year old Tatsumaki is seen inside a prison cell, placed there for not displaying her psychic powers. She witnesses a man defeating a giant multi-eyed monster. His name is Blast. Blast ends his conversation by telling Tatsumaki that she has to be strong, because not everyone can save her. This motivated Tatsumaki to become a hero, and is also the reason why she wants to be alone and cuts relationships with people.

Story Impact

 * Tatsumaki's past is revealed