As Tsuna and Reborn walks to school, a girl arrives and introduces herself as Haru Miura and asks to be Reborn’s friend. After Reborn accepts, Haru asks him if he could hug him but slaps Tsuna when Reborn tells her that he’s a hitman. Haru gets angry at Tsuna for teaching Reborn things about the Mafia and gets angrier when Reborn tells her that he can’t be separated from Tsuna until he becomes the tenth boss. After puching Tsuna in the face, Haru leaves, wanting to protect Reborn.
Later that night, Haru tries to sneak into Tsuna’s house only to see Bianchi who drags her off to eat. As the two eat, Bianchi reveals to Haru that Reborn is a real hitman and Haru sees her eyes filled with tears as she talks about their assassination days.
The next day, Tsuna meets with Haru on a bridge and is surprised to see her wearing some homemade armor. Haru attacks him, saying that she will believe that Reborn is a hitman if Tsuna is able to defeat him. Hayato sees the two and rushes in to help his boss. He throws some of his dynamites which cause Haru to fall down the river. Haru is unable to swim due to the weight of her armor and sees Reborn on the bridge. Reborn uses his Dying Will Bullet on Tsuna and Tsuna is reborn with the dying will to save Haru. As Tsuna jumps off the bridge to save Haru, Reborn shoots two more bullets with his leg screw bullet. After Tsuna saves Haru, Haru has a change of heart and falls inlove with Tsuna instead.
Note: Bold + Italicized = First Appearance