Momo

is an unknown assailant, who is affiliated to the Land of Rivers.

Personality
Momo, like his younger twin sister, is a very sadistic person, delighting in the suffering of others and likewise will taunt them with equal joy. He is also obsessed with power, delighting in the feel of increased might from his cursed seal and finding a good challenge to test his power.

Appearance
Momo has short green hair, light grey eyes with thick eyebrows, grey lipstick applied to his lips, and a pale complexion. He has a collar device based on cursed seals around his neck. When he uses his cursed seal, his skin takes a brown-grey tone, and his appearance takes a monstrous form, his right arm in particular becoming disproportionally big in comparison to his body.

Jūgo Arc
Momo and Sasami confronted and prevented Team 15 from requesting backup from Konoha. Using the opportunity to test their device based cursed seals, they both managed to immobilise Namida Suzumeno and Wasabi Izuno while Sumire Kakei reluctantly escaped with Nue. They later disguised themselves as researchers from the Land of Rivers and brought Namida and Wasabi, both infected with the cursed seal, back to the village, informing Team 7 that they only found the two members of Team 15 unconscious but did not find Sumire. After the Land of Rivers researchers took custody of the incapacitated Jūgo and the entire village turned against the Konoha-nin, he and his sister stood before Jūgo with the head researcher preparing to experiment on him.

Later, after delighting in watching Wasabi and Namida's suffering from their cursed seals, Momo and Sasami were sent to search for the Konoha shinobi wandering in the forest. As they searched, they noticed "Sumire" running by. The siblings quickly pursued her. During the chase, Sasami realised it was a diversion from how their target was deliberately staying just ahead of them. Momo then fell back to the base, intercepting the real Sumire as she escaped with Wasabi and Namida.

Once Momo transformed with his collar, his power proved too much for the genin. Concluding that only Nue's full power would be enough to defeat Momo, Namida and Wasabi offered their chakra to let Nue transform again into its larger form. The gamble proved successful as Sumire and Nue were able to defeat him and destroy his collar.