A young man who sells information for his own enjoyment. He claims to love the entire human race except for Shizuo Heiwajima, and exhibits said love by putting humans in often miserable conditions and observing their reactions. He attended Raira Academy with Shizuo, Shinra and Kadota. According to Shinra, Izaya and Shizuo hated each other with a passion almost from the point they met. In the novels Izaya framed Shizuo for crimes on several occasions. In the anime he puts Shizuo in constant problems, such as gangs attacking him daily up to framing him of crimes. He is a master of parkour, and also quite skilled with his flickblade (the blade he uses must be slightly opened before the mechanics of it springs opens the blade—a switchblade will open on its own after the user presses a switch) as he is implied to be the only one capable of leaving numerous cuts in Shizuo's bartender suit after a fight in the novels. In the anime, he shaves a gang member's head bald without him noticing it. He is also fluent in Russian, which is exhibited in the final episode and episode 13 when he speaks with Simon. Izaya has two younger sisters, Mairu and Kururi, who are twins and troublemakers. He claims to have grown up in a normal family whose only abnormal trait was their naming habits. He does not like his sisters and finds them to be unlovable, saying that if even he can not like them, he expects no one else to ever be able to either. His name comes from a combination of the biblical Isaiah and Japanese for "the one who looks over the crowd." In the novels, Shinra is the only person that Izaya doesn't consider as one of his "humans." Rather, Izaya considers Shinra as his only friend (which is rather rare).

Robin joined the Straw Hat Pirates after Luffy saved her life, or (how she states it) Luffy forced her to live when she wanted to die. To atone for his crime, Robin demands that Luffy allow her to join his crew, to which he complies leaving every other crew member except Sanji in shock. Although feared at first, she is quickly accepted and viewed as a comrade by the crew. Robin is actually an archaeologist of talent, and despises anyone who thoughtlessly damages any piece of history. The World Government fears her because she can decipher Poneglyphs (stones marked with glyphs from an ancient language), which contain details capable of reviving ancient weapons that have the power to destroy the world. In reality, Robin has stated that she does not care about ancient weapons, and that her dream is to find the True History written on the Rio Poneglyph. Robin is a mysterious and serious person who appears quiet and reclusive, and the wisest in the Straw Hat's Crew. She was thought by those around her to be cold and mean, but it was proven that she is actually a kind person who always thinks before she acts. She often only speaks when something interesting or important has happened. She loves to study history, and the comfort and freedom to study and read. She is also quick to point out gross or realistically morbid facts, often creeping out Nami or Usopp. Robin is the wisest and most sensible member of the crew. She has a vast knowledge of the seas and the world, and usually keeps her head during surprising situations, allowing her to logically analyze the situation without losing her cool. This trait makes her different from the other Straw Hats, who often comically react melodramatically to unexpected happenings and hold irrational ideas and conclusions. Despite her attempts to keep herself distant, Robin has fallen for her new friends, and has taken the role of the distant den mother.