Tsuzuki learns that Hisoka is antisocial because of his past. Hisoka came from a well known family and was the only son and that his parents had learned about Hisoka's powers. Hisoka's parents were afraid of Hisoka's powers whe he was young and locked him up in a cage. They told him that he was scary and weren't their son. They thought that Hisoka could see into their minds and hid him from the rest of the world. When Hisoka died in a strange ‘illness' they decided to give him a simple funeral. Hisoka learned that he had to take care of himself and trust no one.

When Hisoka was kidnapped he learned that it was Muraki who had killed him with a curse. Muraki told him that he was only bait to lure Tsuzuki to him. After Muraki shows him what happened the night he was raped and cursed, he is left alone to think. He remembers back to when he met Tsuzuki and that Tsuzuki was so kind to him even if Hisoka was rude to him and called his partner names. He even called Tsuzuki ‘baka' for coming to his rescue when he knew that it was a trap. When Tsuzuki said that he knew and didn't care, Hisoka realised that Tsuzuki really cared for him even if he had been rude to him the short time they had known each other.

When Tsuzuki struggled against the Devil he lost himself in the darkness of his past. The devil reminded him of the horrifying past he had forgotten about. The devil told him that no one cared for him, that no one could forgive him for what he had done. Tsuzuki feel that he is all alone when Hijiri shows up within his dark prison. Hijiri tells him that he likes him and that Tsuzuki shouldn't let the devil fool him. Placing his hands on Tsuzuki, he shows that he really likes him. He then tells Tsuzuki to show the devil what true power is and Tsuzuki breaks out from his prison.

When Tsuzuki is seriously wounded by Muraki's monster while protecting Hisoka, Hisoka holds him close and refuses to let Muraki have him. He is chocked when Tsuzuki used his ability to read minds, asking him to lend his body to the older shingami even though it might hurt. Hisoka hesitates, saying that it might be dangerous but gives in when Tsuzuki says that it is the only way to get rid of Muraki. The power of their trust to each other shows when Hisoka and Tsuzuki fusion and call forth Suzaku. Muraki is chocked to discover the power the two possess.

After Queen Mary blows up, Hisoka and Tsuzuki sits in a helicopter that will take them back home. Hisoka is in tears and shows Tsuzuki his hands. It turns out that Hisoka had been asked to kill Tsubaki when she was dying. Knowing that she was in pain Hisoka had done as she had asked and shot her with Muraki's gun. Hisoka felt regret for doing so and tells Tsuzuki that the blood won't wash of. He buries his face into his hands and cries. Tsuzuki, feeling Hisoka's pain, holds his partner close, showing him that he was there for him no matter what.

After being lured to a play by Muraki, Tsuzuki learns of his past. Muraki tells him that he wasn't human, that he was a monster that walked on earth. Tsuzuki takes it really hard and believes what Muraki is telling him, slowly slipping into darkness. Tsuzuki takes Hisoka with him to a bar and get drunk. Tsuzuki tells Hisoka what Muraki had said earlier before rushing out from the bar. He bangs his head against a brick wall when Hisoka pulls him back to stop him. Hisoka gets visions from Tsuzuki's past that shows that Tsuzuki was bullied by others in his age. He sees a child Tsuzuki that has been beaten really bad but still smiles when a firefly lads on his fingers. Tsuzuki says that he wanted to be like them, to be human. Hisoka tells him that he is indeed human and no monster and won't let Tsuzuki believe nothing else.