Lime Hosokawa was once Brights sidekick but split up after he became a detective. She then decided to build a costume and became Spark Girl and challenged Shadow Lady to prove to light her love for him.
Lime Hosokawa was Bright Hondas former partner. They use to do demonstration to showoff their inventions. During their time together Lime developed a crush on him but Bright did not reciprocate. When Bright left for Gray City to become a Detective she spent her time inventing a costume and various gadgets so she could become a vigilante known as Spark Girl. Shortly after Lime decided to move to Gray City to find Bright. After reuniting with Bright at a cafe Aimi worked at. She found out he still has no feelings for her and decided to help Bright by capturing and revealing Shadow Lady's secret identity, as well as steal her powers to use them for good. After Bright left Aimi invited her over for tea until Bright returned. As they both talked about Bright they learned more about each other becoming good friends in the process. Bright then decided to let her stay at his place while she is in town. She also left a challenge for Shadow Lady a night ago saying she is number two. Reading this Shadow Lady became infuriated.
Later that night when Bright left she suited up and prepared for her battle with Shadow Lady. She then waited for her Shadow Lady to arrive at the top of a T.V. antennae where she had a T.V. crew ready to record their fight and her footage of revealing Shadow Ladys identity. As their fight begins Shadow Lady is able to dodge her attacks but eventually Lime puts her into a arm hold and reveals she knows her weakness. Shadow Lady then hits her in the gut and tries to get away from her to think. As Aimi is thinking of a way to escape, Lime spots her and throws her baton at Shadow Lady to electrocute her.
As Shadow Lady falls Lime catches her and prepares to reveals her identity to the audience. Lime then rubs the eye shadow off and everyone watches as Shadow Lady costume dissolves. Unfortunately Aimi appears in her Crimson Cat Shadow outfit and revealed to Lime that she put on a extra layer of her eye shadow to protect her identity. Aimi then escapes her grasp but not before shredding Spark Girls costume off to embarrass her. As she is hanging from her Grappling hook Bright comes and rescues her. How she came into knowledge about how to reverse Shadow Lady's transformation is still unclear.
Lime is skilled in martial arts and other forms of hand to hand combat and has the intelligence to build gadgets. When she wears her costume she has access to many gadgets like, electric batons and four grappling hooks which are located on her arms and back.