Setsuhen

Lost Snowflake
When a teenager woke up one morning, she found herself alone and injured, lying in the snow. Her memories were completely gone, no knowledge of her age, name, anything. What more is that her heart seemed to have become frozen like the land in which she woke up. An old man happened upon her and took her in, never speaking his name, simply wanting to be referred to as "Sir". The man gave her the name "Setsuhen" (snowflake) due to her being covered in snow and the light fall of the flakes from the sky when he found her. Occasionally, he called her by a pet name "Seppen" which is another way to say her name.

Seppen
Setsuhen revered the old man much like a granddaughter would towards her favorite grandfather and flourished under his care. He tried to get the teenager to smile, but it was extremely hard since she seemed to have lost most feeling. Slowly, her heart began to thaw for her caretaker as they grew closer. The Old Man also began teaching her the shinobi arts, wanting his "granddaughter" to be able to fight for herself once he was gone. He soon began only calling her by her informal name, Seppen or Seppen-chan. She struggled to grasp some of the basic techniques he taught her, but once she gained control over her chakra, she improved greatly, prompting the old man to teach her higher level ninjutsu. It was at Seppen's insistence that he teach her more besides the usual Suiton, Doton, Katon, etc. She wanted to learn different techniques. The old man complied and Seppen became adept at weaponry and techniques that did not revolve around elements. It was also discovered that her chakra type was Raiton, one of the rarer chakra types. As the old man began to age, he began withdrawing himself from the young Seppen, also dropping the pet name and referring to her as Setsuhen.