Emi Sendou is Aichi Sendou's little sister. She is first introduced in Episode 3. She is very much like a mother, like getting Aichi ready for school in the morning, and making sure he gets home at a reasonable time. She also has a tendency to overreact. She attends Miyaji Academy as an elementary school student.
She cares about her brother a lot and acts like his mother from time to time; often having to wake him up for school and worries about his wellbeing. When she saw how Vanguard changed her brother from shy to confident, she starts to worry less about him though she still went with him to most of his matches to support him and watch his well-being. She doesn't know about Kamui's feelings for her and supports Nagisa's feelings for him. She supports everyone on Team Q4.
Due to caring for Aichi she is mature for her age, as well as intelligent and a serious student, as seen in both her card fight ability and her pushing Aichi to do homework with her.
She is introduced in episode 3 when she woke Aichi up for breakfast. She tells Aichi to hurry for school. When she came downstairs, she noticed that Aichi was already at the door and went on his way to school. She was surprised and their mother told her that Aichi's been coming home rather late than his usual time from school. She notes that maybe Aichi finally found a hobby to enjoy. Emi follows him for a bit before Mai came to say hello to her. Later when she was walking home from school, she remembered their mother saying something about a hobby that Aichi had found. She then went to visit her brother's school noticing that it was different from her school. She hid behind the gate when her brother came out and noticed when two other students started to talk to Aichi. She couldn't hear what they were saying, but from what she was seeing, she though that they were harassing her brother. She then followed her brother and the "bad" students to Card Capital. She was surprised when she entered the shop. Shin Nitta appeared from behind surprising her while welcoming her to the shop. He then noticed that she was looking at the tables and explained to her that what they were watching was the newest card game called Cardfight Vanguard which is becoming quite popular. She then noticed Aichi on one of the tables and saw a change on her brother that she never seen before. Shin explained some rules about Vanguard when they were watching Aichi fighting Morikawa. When she saw Aichi winning against Morikawa, she noticed how confident he was from playing this. Then she asked for them to play again.
In episode 5, she once again appears only to bring Aichi home from Card Capital. She later on appears at the end to yell at Aichi for being at the shop again.
In episode 11, she brought lunch for Aichi and his friends to enjoy. She later on stayed to watch Aichi's match against Kamui in episode 12 and 13.
In episode 15, she was walking home when she was reminded of Card Capital so she went there for a visit. She was greeted by Nitta and the Manger. She then noticed the Vanguard booster packs and Nitta asked if she wanted to learn to play Vanguard. When Aichi and his friends came to Card Capital, she told Aichi that she was going to learn to play Vanguard. Morikawa decided to teach Emi how to play by playing a match against her. On her match against Morikawa, she only used the "cute" cards from Misaki's deck causing her to not use Lozenge Magus throughout the match. Kamui decided to help Emi with some tips though Nitta wanted her to learn to play the cards by herself. She won against Morikawa.
In episode 18, she brought lunch for everyone and stayed throughout episode 18 to 22. She supported Team Q4 from the stands.
In episode 25, she helped Shin bring Misaki the happier memories of her childhood by playing a match against with a trial deck. Emi told Misaki that it was fun playing this game making Misaki remember her mother and father smiling and herself as well.
During the national tournaments, she accompanied Team Q4 as they fight and supported them from the stands. Later on she stayed with Aichi while he was recovering from using his powers during a match. She stayed for the rest of the tournament, cheering for Team Q4 for winning the championship.
In episode 34 and 35, she joins Team Q4 as they train with Team Caesar.
In episode 37, she cosplays as Princess Maiden from Team Overthrow. She uses her Bermuda Triangle deck.
In episode 51 and 52, Emi joined the Card Capital tournaments. She uses her Bermuda Triangle deck throughout the tournament and wins the Junior division.
Emi stayed behind with the rest of the crew at Card Capital during the first two stages of the tournament (Singapore and Seoul). She accompanied team Q4 and watched them fight during the Hong Kong stage. She then accompanied team Q4 and watched them fight in the Japan stage.
Emi becomes a middle school student at Miyaji Academy. In episode 114, she, Mai, and Rekka created a club for Vanguard in the Miyaji Middle School. The club is called the Vanguard Cardfight Circle, when Shingo Komoi and Naoki Ishida came. Naoki and Mai played against each other. After the battle, Shingo and Emi faced each other, ironically cardfighting over how Emi talks to Aichi. Emi manages to win using the new Bermuda Triangle units.
When Kai goes to Card Capital to find out no one remembers Aichi. He sees her cardfighting Mai and asks her about her brother, Emi responds by saying she's an only child, shocking Kai.
In episode 175, she makes a cameo appearance at the beginning of the episode cardfighting Mai. When Shin asks her who got her into playing vanguard, she remembers it was someone in her family, but is unable to recall exactly who, due to her memories of Aichi being erased.
G Season 2
Emi is seen in Card Capital watching the G Quest announcement along with Miwa, Misaki, Morikawa, Izaki, and Naoki. She is seen in Episode 14 when she joins a shop tournament in Card Capital #1. Still playing with the Bermuda Triangle clan and its cute cards, she wins against Tsuneto Tado, but loses to Chrono Shindou during the finale. She is still oblivious to Kamui's feelings.