Ichigo Kurosaki vs. The Assassin

 is a fight that takes place on the roof of Rurichiyo Kasumiōji's home.

Prologue
The strange young girl from the day before mysteriously shows up in Ichigo’s class dressed as a student. She is surrounded by the older men from before, who are also wearing uniforms in order to blend in with the other students of Karakura High School. The little girl introduces herself as Rurichiyo Kasumiōji and names her companions as Kenryū and Enryū. She will only speak with Ichigo and initially wants to walk home with him and his companions. However Kenryū bribes her with the promise of sweets to abandon this.

That evening at dinner, Rurichiyo appears smitten with Ichigo, much to the bemusement of Kenryū and Enryū, whom she tells to stop worrying about her so much. At Ichigo's, Rukia, Ichigo and Kon discuss the three newcomers and how everything surrounding them is a mystery. They decide to sleep on it, but later Ichigo and Rukia feel the Reiatsu of some sort of adversary close by. Upon investigating, they discover Kenryū upon his roof dressed as a Shinigami and initially believe it belongs to him. Before anything can be discussed, a bright light appears and an intruder forces its way through the roof. The three of them investigate, but Kenryū jumps out of a window and runs away with Enryū, who is carrying Rurichiyo upon his back.

Battle
At first the intruder tries to evade Ichigo and Rukia by heading to the roof and towards Rurichiyo, however, he is pursued by both of them and Rukia surmises that the others are clearly his target. Agreeing, Ichigo swings his Zanpakutō towards the intruder, who blocks with his own weapon as Ichigo demands to know what he wants with the young girl. However, the mirror on the intruder’s weapon uses light to blind and stun Ichigo so that he can defeat him. Ichigo recovers just in time, with his sleeve being cut in the process. The intruder turns its attention to Rukia and uses the same technique on her, but Ichigo prevents the intruder from hurting her.

Rukia realizes that the light is more than blinding them and tells Ichigo to be careful. Despite this, he is caught once more in the technique, forcing Rukia to come to his aid and engage the intruder herself. She informs Ichigo that she believes they are dealing with an assassin and for him to not look into the light. However, Rukia is cut while fighting the assassin, and Ichigo once again takes over the battle. Ichigo closes his eyes and reflects the light back onto his opponent and swiftly disarms him. After explaining how he won, Ichigo demands to know why the assassin is after Rurichiyo, but the assassin begins to flee. Thus, Ichigo is forced to use Getsuga Tenshō to stop the fleeing assassin and the resulting explosion kills the assassin.

Aftermath
Ichigo and his friends soon discover the reason for their mysterious behaviour. Rurichiyo is the heiress of one of the most powerful noble clans in the Soul Society, the Kasumiōji Clan, the highest noble family that is not one of the Four Great Noble Clans. They explain that Gyōkaku Kumoi, one of the clan's vassals, has been behind several recent assassination attempts on Rurichiyo’s life in a bid to become leader of the clan. For this reason, Kenryū and Enryū took Rurichiyo to the World of the Living in order to protect her from assassination and request Ichigo’s aid in this.