|Physical and Vital Statistics|
|Manga||Volume 3 Chapter 9|
Kusakabe appeared when he wants Erika Shinohara and her friends to pass up their math exercise book. Then later Erika meets him in a supermarket while she wants to buy the ingredients to make chocolate for Kyouya Sata. Very Insecure and Erika tells him he should be more confident and also tells him to show his face more instead of hiding it behind his hair bangs. His face is mostly hidden in both the anime and manga with his hair to show his insecurity.
Kyouya even got jealous when he saw Erika gave one of her chocolates to him during Valentine's Day when those chocolates were meant for Kyouya. After Erika and Kyouya decide to be just strangers again Erika start's hanging out more with Kusakabe at school and out of school and Kyouya's see's them together and this makes him even more jealous and also makes him realize his true feelings for Erika.
Kusakabe is an unconfident and shy outcast, who is deemed a "coward" and "herbivore" by Kyouya Sata that Kusakabe is also very negative. After Erika Shinohara got to know Kusakabe, she realized that he is a nice guy and he just needs a bit more confidence. Erika is also the one who made Kusakabe more confident as shown in later chapters of the manga as he also does a speech at the graduation ceremony in their final year and Erika cheers from in the crowd.
When Kusakabe was in elementary school, he often get bullied and laughed by the other pupils because of his girly face and his elementary school classmates also call him ghost due to his pale skin. His sister and mother are worried for him thinking he would never get a girlfriend or ever receive chocolates or gifts on Valentine's day.
Kusakabe is first seen in Episode 6 as he tries to collect math books from Erika Shinohara, Aki Tezuka and Marin Tachibana (Kusakabe's classmates). Due to his quiet voice, he cannot be heard over them, and turns to leave. However, Erika notices him and approaches him, asking if there's something he needed. He asks for her math note books and Erika says she will gather them later. It is noted his classmates think he is quiet and timid.
Erika later sees him in a supermarket while she is standing in line. The other customers are impatient as he searches for his wallet, only to find out it's not on him. He is embarrassed and says he will take the groceries back.
Witnessing this, Erika quickly offers to pay, saying he can pay her back later. Kusakabe is taken aback by her kind gesture. As they leave the store, he apologizes and says he will get the money right away. Erika responds by saying he can pay her back tomorrow, and that it's fine. Kusakabe apologizes again, saying he caused her trouble and that they're not even that close. She responds kindly by saying she's not the type to leave a person in trouble. Kusakabe thanks her and Erika remarks about his eyes without his bangs in the way. He again apologizes, saying he thinks he makes people uncomfortable because of his appearance. Erika is shocked by his negativity and comforts Kusakabe, saying she wants to make him her cell phone screen saver and stare at it. He is embarrassed and denies her compliments. Erika tells Kusakabe he should be more confident, and that no one would be uncomfortable looking at him. He thanks her, saying he will work on it.
The next day, Kusakabe is seen greeting Erika as he tells her that he was able to say good morning to others. Erika responds saying that she was right, and all he needed was a little confidence. He smiles and says "You're right. Maybe I'm the one being too cynical." Erika steps forward and moves his bangs out of his face.
Kusakabe blushes and looks shocked as Erika remarks he would be popular with the girls if he pushed his bangs back. Kyouya Sata sees this, and walks up to her, bringing her close to him. Erika blushes and looks to him, asking what was wrong. Kyouya says he was cold, and she was very warm-blooded. Kyouya proceeds to tease her in front of him, and Kusakabe seems saddened as he walks away, Kyouya seen smirking.
At lunch that day, Erika spots Kusakabe sitting alone outside and goes to talk to him. She asks if he is ok, commenting on how his face was pale. Kusakabe brushes off her worries, and asks her about the chocolates she is holding. She says they are for her boyfriend and Kusakabe says he hopes he'll like them as he looks away sadly. Erika asks him what's wrong and he says he tends to get melancholy around Valentine's, saying his sister and mother start acting weird, and he is concerned that they worry about him not receiving Valentine's day gifts. Erika is sympathetic and gives him one of her chocolates so his family can be at ease. Kusakabe thanks her, and is seen by Kyouya shortly after holding the gift affectionately. Kyouya meets Erika, and once he sees her chocolates, he is shook. He denies her chocolates, remarking that she also gave them to Kusakabe, and to not put him on the same level as a guy like him. Erika is angered and defends him, saying Kusakabe is leagues above Kyouya.
Later on, Kusakabe quickly pulls Erika back before she could fall down some stairs due to her spacing out. She apologizes and Kusakabe offers to listen to her if she wanted to talk. Erika smiles, and then comments on how he's so cool. She begins crying, saying that she hates Valentine's day.
They go to a restaurant where Erika vents about the real Kyouya, saying he is stuck-up and domineering, and how he is nothing like he is at school. Kusakabe apologizes, saying it was his fault since she gave him the chocolate. Erika disagrees, saying that she doesn't believe she was in the wrong there. Kusakabe asks her why she is still with him, and Erika admits she might just be better off without him. He sees this as an opportunity and confesses to her, saying he would never make her cry or worry.
The next day, Kyouya passes him in the hall and Kusakabe asks to speak to him. He tells him that he liked Erika and had already confessed to her. Kyouya replied by saying that he didn't care and he could do what he wants. Kusakabe asks Kyouya if he really loved her, to which Kyouya replied, "A woman like that... she was just a way to kill time from the start." Unknown to him, their conversation had been heard by Erika.
When he invited Erika to hang out with him, Erika invited Ayumi Sanda and Kusakabe was unhappy about that as he planned to spent time together, alone. Later, he propose another invitation to Erika. Erika accepted and both of them went to the water park.
Later, Takeru Hibiya saw both of them and called Kyouya. Both of them went to water fountain when Erika rejected him when Kyouya stood behind her.
Yuu stated that he didn't regret falling in love with Erika.
Kusakabe fell in love with her once but she rejected him. He kindly accepts their relationship and warned Kyouya to not hurt Erika, again. Many people in both the manga wished to see Erika and Kusakabe together. Everyone thought that Kusakabe treated her much better than Kyouya. However, it helped their relationship mature.
Kusakabe looked at him as a rival at first. However, Kusakabe later calls him a "friend".
- The name Yuu (憂) means "anxiety".