Their appearance is very different from each other as Parenza appears short and a bit fat while Tras is tall and skinny. Parenza seems to be the leader, as Tras talks to him in that way.
Parenza and Tras were seen when Verde asked them to assassinate the Vongola 10th candidate, Tsunayoshi Sawada, with a poison. They managed to get inside the house, but as soon as baby Hayato Gokudera saw them, he used his Bombs; however, they failed, because Giannini had remade them. Ryohei Sasagawa and Takeshi Yamamoto fought them but lost because they got trapped. Parenza and Tras grabbed baby Gokudera and will kill him if Tsuna didn't come to him slowly. As soon as he almost got there, Basil and I-Pin came and fought them and won with the help of Ryohei and Yamamoto when Basil cut the trap with his Triangular Blade.
- In the manga, Gokudera is helped by Yamamoto to deactivate their camouflage, and Tsuna defeats them by himself.