+ ++ Lenne and Yuuna|
People say that Lenne is just a Yuuna wannabe and that Squaresoft just ran out of ideas for looks. But the real reason behind the resemblance are that when Yuuna found the dress sphere, she became Lenne. So it is easier to understand that Lenne looks like Yuuna because in a way, Lenne is Yuuna 1000 years ago. Lenne's soul lives in Yuuna's body. Whenever Yuuna uses the dress sphere, she becomes Lenne: heart, soul, voice, and she has her memories. That is why many people saw Yuuna singing. Yuuna relives Lenne's life and she gets dreams and in her dreams, she is in Lenne's shoes and Tidus is in Shuin's shoes. She dreams of Lenne's and Shuin's death. She is running away with Tidus and when they are cornered, they stare into each other's eyes like Shuin and Lenne did. When they got shot, Tidus doesn't move but Yuuna tries to reach out to Tidus. But during Lenne's and Shuin's death, Shuin was the one that tried to reach out for Lenne but Lenne just cried and moved her hand a little. Both of the scenarios are quite similar but Yuuna acts a bit like Shuin more than Lenne but she is still in Lenne's shoes.
Yuuna lost Tidus but in FFX-2, Shuin loses Lenne. They both cannot except it but Yuun could accept Tidus' death more than Shuin could accept Lenne's death. Shuin searches for Lenne and Yuuna searches for Tidus. Yuuna successfully defeated Sin while Lenne didn't even finish her pilgrimage. Yuuna brought the Eternal Calm but Lenne didn't bring anything.
Because Lenne's spirit came back into Yuuna's body, that is why Shuin reappeared. The reason why Shuin is in his body is because he was unsent. Lenne didn't have to be sent and her body perished 1000 years ago, so she used Yuuna's body to talk to Shuin and stop him from doing anything unnecessary (such as using the Vengagun. Shuin doesn't know that Sin was defeated).
Lenne's features are just slightly the same as Yuuna's. They both have earrings, brown hair, skin color, clothes, and not to mention: beautiful. Lenne's hair is longer and it is slightly layers at the front. Yuuna's hair is short and layered and has a flair on the tips and a long ponytail. Lenne's earrings are longer and brightly multicolored and Yuuna's is shorter but they are both made from beads.
The reason why Lenne is in Yuuna's body instead of anyone else's is because Yuuna found the sphere and the connection is probably stronger between Lenne and Yuuna because they were once summoners and also they have links to the spirit world unlike most people.