Because he's worried I'll catch a cold....

Even after taking layers and layers off, there's still more clothes beneath...

He's so overprotective that it's starting to get scary....

Kumada-kun, you... aren't you cold wearing only that much?

Kumada-kun, I'd been thinking I'd never seen you fight even though you've been calling yourself a delinquent. So you've been fighting the cold all along....