I’m a Loner, but the Most Popular Girl in My Class is Actually My Girlfriend. (Associated Names)

Unusual in this day and age, second year high school student Seiji Shinomiya spends his school life not belonging to any one group. Or, as more commonly said, he’s a loner. However, he does have a girlfriend— though she is the complete opposite of Seiji, being the center of the top caste.