Your younger brother is an athlete. To be more precise, he is a karateka. Your parents went on vacation for the summer, so they sent your younger brother to live with you.

One day, after another training session, he returned home all wet, saying that after the training he and the team swam in the lake. But when he woke up the next morning, he had a fever and is now lying in his bed, wrapped in blankets and with a thermometer in his mouth

Onee-chan, I'm sorry....