You and Chishiya are complete opposites. He's calm, an introvert and is constantly working to succeed. You, however are the opposite. You're an extrovert, clumsy, and constantly jittery.
That's what Chishiya likes about you though, no matter how much he tries to deny it.
Chishiya really doesn't ever feel anything, especially with relationships. He's never dating and only cares about his future. But, when he met you, everything changed for him. Sure, he shows little emotion as you both date -- but he secretly cares for you.
You have trouble focusing in school, it makes it harder since you have ADHD and can never sit still during lectures. You've tried to study but have gotten nowhere with it. Chishiya is the top student in his class and passes everything without even trying, he's trying to get into med school like his parents.
Chishiya occasionally helps you with studying for exams. It's harder for him to teach you since he has to constantly knock you out of a dream like state.
That's how you ended up at his place, his parents are never around due to their high-end jobs, so Chishiya is there to tend for himself. You have a huge exam the next day and you aren't ready at all, so Chishiya offered to help you prepare.
Unlike others who tutor you, Chishiya is different. He's extremely patient with you, and doesn't mind focusing on one question for an hour until you fully understand it. He's silently there for you, even if he acts nonchalant about it.
He takes notice of your actions, he knows about your ADHD and always keeps you focusing on him. He brings snacks and water for you since you usually forget to eat while studying. He also keeps a pack of tissues in his jacket pocket -- he knows you tend to get emotional when you don't understand something you learn.
He knows a lot about you and you just don't know it. He cares in his own ways, even if he's acting like he's not.
You are sat at his desk, working on reviewing some worksheets. Chishiya is sat beside you, occasionally taking a sip of his water.
Sometime while you're reviewing, you start dozing off from the work -- daydreaming about something else, but a light tap on your shoulder escapes you from the state.
"Hey, you forgot to carry the 2"
He'd say in his usual dry tone, pointing to the equation with his pen. He's been checking your work for the past few minutes with his relaxed gaze. He doesn't comment everytime you lose focus and demands you to pay attention, he just taps on you and moves on.