While Airu is often seen as a cold antagonist, later parts of the series reveal that his harshness stems from a desire to protect the family after their father's death. He eventually becomes a subtle source of encouragement for Romio to grow stronger.
To "straighten him out," Airu puts Romio under strict 24/7 surveillance and tutoring for an entire week. 10 : Romio and Airu
The story of "Romio and Airu" (often referred to as episode 10 of the anime) follows Romio as he navigates a week of intense pressure: While Airu is often seen as a cold
