Luini was described as a man of slim build in his twenties, between 185 and 190 cm tall, and with a large crescent-shaped scar on his left cheek. He has prominent teeth, a high brow and fair, combed-back hair. During his killing spree on the boat, Luini disguised himself as a Kakin soldier. Afterwards, he switched into a tracksuit similar to what Phinks usually wears.
Luini is a ruthless killer. He murdered 20 people in a short span of time, and later killed another as a "prank" for the Phantom Troupe, for whose fearsome power he feels an intense feeling of adoration. Like his leader, Morena, he appears to want to destroy the world.
When Morena became the Boss of the Heil-Ly family, she ordered that her underlings kill each other until only 22 were left. Luini survived and agreed to follow her.
Luini willingly boards the B‧W1號 to follow Morena, who kisses him to activate her ability. Luini disguises himself with a Kakin soldier and goes on a killing spree, murdering 20 people in Tier 3 with an edge weapon. After the massacre, 卡修 offers to mix lies and truths in her account. Luini insists on her giving an accurate testimony about his scar, in order to fully assess the royal army and 獵人協會's investigation capabilities, convinced that even if he should be caught, he will be able to escape. Feeling a spatio-temporal power awaken inside of him, he locks himself in the bathroom and activates his ability.
He next appears in Tier 5, spying on Nobunaga, Phinks and Feitan while they are inside a warehouse. He swiftly grabs their guide, slits his throat, and drops him behind them. When they ignore his actions, Luini admires their composure and wishes to destroy the world with them. He goes back to kill the other Mafia members in the warehouse, except for one, whom he gravely injures. He carries him to the 加•夏家族's hideout and is let in, then teleports again.
Knife: Luini's weapon of choice is a knife with a blade more than twice the length of the handle. Outside of combat, he uses it to activate his Nen ability.
Luini was able to kill 20 people in a short amount of time with an edge weapon, which suggests a certain amount of skill. However, according to Feitan, his handling is crude. Luini was also one of the 22 survivors after Morena had her underlings kill each other. He appears to be quite fast, snatching the Phantom Troupe's guide inside the warehouse in a split second. He appears to have some planning and infiltration aptitude, as he successfully disguised himself on two separate occasions, managing to sneak into the Cha-R Family's hideout on the latter.
| ||Luini can activate his ability only while locked into a room with a single door and no other exits. After fulfilling this requirement, he can cut open the walls of the room with his knife and enter an alternate dimension which allows him to travel to any location he has visited in the past, including outside of the Black Whale, emerging from another surface. He is also capable of returning to the locked room at any given moment; however, if the room is opened, the ability is reset and Luini is unable to use it on the same room again. He can also open a gash in a surface, such as a ceiling, to observe a target from the safety of his alternate dimension.|
- The second half of his name (ニー) is very similar to the Japanese numerals for 2 (二) and 1 (一). Coincidentally, 21 is his level at the time of his introduction.