Sons of Liberty stemmed from the developer's desire to develop Snake from a third-person perspective. Kojima stated that Raiden's character and his perception by the audience were important to the overall feel of the story. The idea of having a second main character was inspired by the Sherlock Holmes short stories and novels in which the narrator is Dr. Watson rather than Holmes. Kojima said Snake was the game's protagonist rather than Raiden. Yoshikazu Matsuhana, assistant director for the project, was uncertain about this decision; he considered Raiden a "weak-looking character" but decided to follow Kojima. The codename "Raiden" was based on that of the Mitsubishi J2M Raiden, a historical combat aircraft of the Imperial Japanese Navy Air Service. It was initially planned to be written in katakana as "ライデン", but was changed to the kanji form "雷電" because of a resemblance to Bin Laden's "Laden" in katakana, "ラーディン". His full name was going to be "Raiden Brannigan" but the idea was scrapped. The romantic relationship between Raiden and Rosemary was inspired by Kojima's experiences; their names, Jack and Rose, are a reference to Leonardo DiCaprio and Kate Winslet's lead characters in the film Titanic. In Metal Gear Solid 2, Raiden is considered to be a representation of the player through the experiences between the player and the character during the game. Kojima received much fan mail; one letter from a girl stated she did not want to play a game with an old man. Kojima took this into consideration; he and his team designed Raiden to be more appealing to women. Designer Yoji Shinkawa said he and the other character designers took much inspiration for Raiden's appearance from the bishōnen archetype. Because Raiden was a new character, the staff designed him carefully, giving him white hair to symbolize his introduction. Shinkawa also said Raiden had an overall feminine appearance. His outfit—the Skull Suit—was difficult to design until the staff decided on a "bonelike" concept. Shinkawa wanted to make Raiden sexually appealing, emphasizing the tightness of his clothing. The design of Raiden's aqua-mask was inspired by ancient mystical ninjutsu, where the ninja bites a scroll in the mouth during magic transformations. Raiden's final duel with the boss Solidus Snake was revised in the making of the game. Originally, to defeat Solidus, Raiden must cut off both his mechanical snake-like arms, then he must attack Solidus' back and sever the backbone