Producer Yuma Takahashi had similar opinions, believing the style of some scenes that symbolize their romance were needed. Singer Aimer wrote the theme song "Hana no Uta", which focuses on Sakura. Having not known of the character before the making of the film, Shitaya was surprised when learning of Sakura's characterization as she discovered new traits about her. Aimer's theme song "I beg you" was written to explore the relationship between these characters; Aimer wanted to show Sakura's dark personality because she wants Shirou to love her but does not want him to know about her secrets. The author of the printed adaptation of Heaven's Feel noted that for the serialization of the manga he wanted to start the story between Shirou and Sakura with the first time the latter met the former and fell for him in contrast to the original visual novel which left this scene until some scenes more in the route. Shitaya enjoyed Shirou's noticing of Sakura's feelings. Shitaya enjoyed the exploration of Sakura's feelings towards Shirou, which she said brought a new level of depth to the character. English voice actress Cristina Vee said that in preparation for the dub of the film that Sakura is "very quiet and meek, so she's going to be very scary". Sakura is introduced in visual novel "Fate/stay night" as a first-year high-school student and the sister of Shinji Matou, a friend of the story's protagonist Shirou Emiya. After Shirou's father Kiritsugu dies, Sakura often visits Shirou's home to help him with his daily chores. Though Shinji is from a family of sorcerers, Sakura has no knowledge of her family's craft and history. Sakura is outwardly shy and has a long-standing and obvious crush on Shirou. Sakura plays a minor part in the "Fate" and "Unlimited Blade Works" routes. In the "Heaven's Feel" route, however, she is the story's lead heroine and her backstory is vastly expanded. In the anime-original storyline, Sakura is kidnapped by Caster as a sacrifice to summon the Holy Grail because she has latent magic circuits. During a rescue attempt, she and Rin are confirmed to be sisters who were separated in early childhood. Sakura is proven to be a powerful mage as well as Rider's true Master, having used a command spell to give control to Shinji because she had no desire to fight. Her brand of magic is unique; she cannot command any of the five traditional elements but can manipulate the very rare Imaginary Numbers, which are connected to demons.