Yūka Amino (網埜 優花 Amino Yūka) is a classmate of Saya Kisaragi who acts as an older sister figure, chastising Saya for being late or distracted while also caring about her.
Yūka has the appearance of a tall fair-skinned teenager with chin-length black hair that has a fringe cut on the right side, dark-colored eyes and nude lipstick.
On terms of clothes, Yūka mostly wears her school uniform.
At the end of the series, after the deaths of the Main Cast, it is revealed that Yūka is actually a woman in her mid to late twenties.
In "Blood-C: The Last Dark" movie, Yūka now appears more her age: she wears a formal suit of a grey blazer with a turquoise blouse underneath, a dark grey pencil skirt, black hose and blue heels. She also wears a necklace and red lipstick.
Yūka is shown to have great annoyance at Saya Kisaragi for being too soft and always helping people (the reason she comes to school late) which causes her to get angry, but she is still kind despite her hot headed nature.
In reality, Yūka is actually a cold woman who will do anything to achieve her goals and shows little value toward human life.
Yūka is first seen when Saya Kisaragi comes into the classroom and states that she made it on time. Saya states that it had some trash on the road but she put it in the trash area so it would be fine. Yūka yells at her asking how she could be such a softy. The twins then start to tease her saying she was scary and she acted like an overprotective mom making her more angry (in a comical fashion). They are interrupted by Itsuki Tomofusa who tells them that the teacher would be coming soon and that they should continue their little routine later.
After P.E, Yūka asks Saya if she was always good at sports because she was so good at it. Saya says that her mother was dead and her father was almost always busy with the shrine so it wasn't ever like that. She then goes on to explain her mom's death and how Fumito Nanahara gave her boxed lunches to cheer her up. Yūka then states that Fumito and her father must be good people and Saya with a smile says yes. After school she is seen with the twins watching Saya leave the classroom and she turns around and says bye.
The next day, she is seen when Saya started to talk about the dog she saw on her way to school. Yūka said that it must have been abandoned but Saya disagreed saying it was too bold.They are again interrupted by Itsuki and Saya tells him good morning. He says that she should call him by his name instead and Saya says that she could call him class rep Itsuki and he says that that wasn't what he meant. At lunch time, Saya, Nene Motoe, Nono Motoe & Yūka were eating their lunch together (a plan set up by Itsuki to get closer to Saya) until Saya saw Shinichirō Tokizane and went to greet him. After she finished talking to him, Yūka told Saya to hurry up because they were almost finished eating. The next day, Yūka is seen with Nene and Nono as they run up to Saya and asked her if they could go somewhere. Yūka said that their wasn't anything interesting in the town and they both said she was mean. Saya then notices Itsuki and he comes over to ask her what she wanted and Saya asked him what was the name of the place he said had good cakes.
After he said that, he was talking about Cafe Guimauve but stated that he was glad she refused to go last time. Yūka asks why and Itsuki says that he would have looked like an idiot because he acted like he knew the place and she was a regular customer there. When they decided they were going, Yūka told Itsuki that sending Saya to the cafe may have worked and he just laughs. They walk down the road and stop when Nene and Nono started to complain about how boring the town was. Saya then comments on how they talk good simultaneously and Yūka says that they're like a comedy routine. Nene and Nono said that she could have said they acted like an idol or a band but Saya says she doesn't know what they were talking about since she doesn't have a TV (which everyone expressed shock at).
At the cafe, Yūka commented that she doesn't really like cake but the one she's eating is good. After, Itsuki said that he liked to cook but says that Saya would probably take it the wrong way, Yūka is seen looking at Saya with Nono. When Saya asked what they were looking at Yūka just sighs at her on the back. Soon after a policeman came and told them to go home before dark since the Nightingale Bakery's owner went missing and after they left, leaving Saya.
The next day, she is seen walking to the usual spot to eat lunch with everyone else. After Nono states that the baker must have just gotten tired of the countryside and ran away, Yūka asked if it was still called 'running away' even when you're an adult. Nene asked what else you would call it and when Itsuki said it, they replied that that was the correct answer. Yūka along with everyone else watches as Saya chases after the dog she's been seeing recently and later Nene asked where she went but Yūka replied that she doesn't even know.
In Episode 9, she is killed among several of Saya's classmates by the Spider Elder Bairn. Like Nene and Nono, her death was fake due to the fact that she was a part of the main cast.
In the last episode, Yūka was the only survivor of the main cast who was rewarded by Fumito and her wish to become the next governor of Tokyo came true.
Yūka and Saya were close friends. Sometimes she would scold her for always being so late, or just on time. They appear to have a strong bond within the manga as Saya cried after her death by the Spider Elder Bairn and thrown off the roof of the school.
The twins often insulted Yūka by calling her scary like their mom. However, they were friends but as they were all in the Main Cast it is unknown how they really felt about each other.
- The name Yūka means "excellence, superiority, gentleness" (優) (yū) and "flower, blossom" (花) (ka).
- Yūka's surname Amino means "netting, network" (網) (ami) and "open country, field, wilderness" (埜) (no).
- Yūka is the only member of the "main cast" to survive.
- Masumi Asano described Yūka's initial character as a rough and loud person with a kind heart.