The supporting characters include Miyamura's friends and family, and Hori's friends and family. Here's some information on all characters: (if on mobile, please swipe)

Student Council members

 Sengoku Kakeru - The club president is Hori's childhood friend and he knows all of her embarrassing stories. He has red hair and is quiet weak. He's also bad at sports and is uncomfortable with how skinny he is. 
Ayasaki Remi - The next council member is a cute girl with pigtails. She's the president's girlfriend and is weaker than the president. She always messes with Hori about stealing Miyamura and succeeds every time.
 Kouno Sakura - The final member is a girl who doesn't believe she is cute, she has short hair, glasses, and loves to cook. Her best friend is the president's girlfriend. She has a crush on Miyamura's friend and often bakes things for him.

Hori's friends

 Hori's best friends is a cute girl who always wears large sweaters so that the sleeves cover her hands. She's kind and also has a crush on one of Miyamura's friends.
 The president has already been explained.

Miyamura's friends

 Friends since middle school and Miyamura always acts kind of violent around him. Miyamura believes the reason why he's not the boring person he used to be is because of this person. He has sort of spiked, long hair. His eyes suggest mischeif and he's the one Miyamura goes to for relationship advice.
 Friends thanks to Hori and doesn't seem to jealous that he wasn't the one to get her. He knows Miyamura's secret about his tattoos and piercings and has even visited Miyamura's home. 

Hori's family

 Usually, Hori just lives with her younger brother. He looks just like their father and has gray hair. He loves playing sports and often stays after school to play football with his classmates and friends. He loves anime and is a pure kid. 
 Hori's mom looks just like Hori and is said she looks quiet young. She is very supportive of Hori's relationship with Miyamura and is hard-working.

 Hori Kyousuke - Hori's dad is huge and looks like a bad fellow, but is actually a man with a sense of humor and family. He's also supportive of Hori's relationship with Miyamura and is already calling Miyamira his son-in-law. 

Miyamura's family

Miyamura's mom shows up rarely, but is OK with Miyamura's piercings. Along with her husband, she runs a bake shop, which was featured on a magazine.