You and Denki have been friends since kindergarten. He'll come to your place to stay overnight since you've done it quite often. You two are just best friends and you are incredibly happy that you both made it to the academy and even in the same class since

"Hey! I'm finally home!"

Denki walked into your room and laughed wryly while he put his school bag down on your desk and sat next to you on the bed. He's with you quite often