Some academic geniuses suffer from burnout. Others simply lose all interest in their studies and want to focus on other things. Junichirou Kagami falls into the latter category. He was once a teenage physics genius whose papers were published in Nature, Science, and other prestigious research journals. Unfortunately, upon graduating from college, he left the science field and became a shut-in whose life motto is "I can only do things I want to do."

These days, Kagami spends all of his time watching anime, reading manga, collecting figures, and updating his blog. He seems satisfied with not having a job, but his younger sister, Suzune, cannot stand the thought of her brother being an unemployed loser for the rest of his life. She goes behind his back and gets him a job as a substitute teacher at his old high school. What lucky timing that the regular physics teacher had to go on maternity leave! And good thing his alma mater remembers him as that teenage genius! But can a hardcore otaku actually teach a bunch of high school students anything important and useful?