Ni and Li

Ni and Li are two of Riser Phenex Pawn.

Appearance
Ni and Li are young girls in appearing in their teens, Ni has red eyes and blue hair while Li is the opposite with blue eyes and red hair. While Ni ties her hair in a ponytail, Li ties hers in a braid. both have light brown cat ears with black stripes and each having piercings one of the ears opposite each other, Li has two golds on her left with Ni having blue colored on her right. The appear to be the same hight in the anime, although in the manga one appears shorter than the other.

Both girls wear short skimpy white sailor uniforms that reveals their abdomen, shoulders and lower breasts and black skirts, the also wear their ascots in different fashions. They're always seen wearing red and blue fighter's glove matching their hairs respectively.

Personality
Both appear to be equally cheery and childish even during a fight. They also show a feline personality, sometimes speaking with "Nya" (にゃ), mimicking a cat's meow.

History
Not much is known about Ni and Li, other than at some point before the series, they were revived as Devils by Riser.

The Red Dragon Emperor's Awakening
Ni and Li first appeared in Volume 2 at the Occult Research Club, when Riser introduces his peerage to Rias after the their master decide to have a Rating Game against Rias to solve the engagement between the two. During the Rating Game, they fought against Issei along side Siris and Mihae, but were all retired from the game with the combined abilities of Issei and Yuuto.

The Legend of Oppai Dragon and his Lively Companions
In the Extra Life of DX.1, Ni and Li participated in their masters rematch against Rias. They both wanted to get pay back on Issei for last time but Koneko intervened wanting to take them on due to als instead, the two were eventually defeated by her.

In Volume 19, both Ni and Li participated in the Rating Game between their master and Diehauser Belial.

Powers and Abilities
Promotion: As Pawns, Ni and Li can use promotion to temporarily gain the traits of a Queen, Rook, Knight, or Bishop.

Heightened Senses: As Nekomata's, Ni and Li naturally have great senses such as smell and hearing.

Hand-to-Hand Combatant: Together two are shown to be skilled in close combat which they use along with their heightened reflexes which they're also shown to be be quick and agile.

Senjutsu Users: Being Nekomata's, they're especially skilled utilizing by controlling the flow of Ki that could strengthen their physical abilities.

Trivia

 * Ni and Li are one of two pairs of twins in Riser's peerage, alongside Ile and Nel.