Gen reached to tug some of those scraggly bangs that hung from Senku’s head, just a playful little gesture. “That’s called sleep, my dear demented genius. And I do worry you’re not even getting those eight hours when I’m not there to supervise.”

He’s teasing. A little, anyway. Hearding Senku away from his work was something he had to do a bit when they were younger. Apparently he didn’t need to reinvent caffeine to try and pull all nighters.

“Ryusui-chan is too easy,” Gen sighed. “I can get whatever I want from him. And what’s good a vacation if I have no-one interesting to talk to, my dear?”