The Anime Lad
Taiyo is a shy high school student who can speak comfortably only with his childhood friend Mutsumi. Their bond attracts the hostility of her fiercely overprotective brother, Kyoichiro. Mutsumi's home life is tied to an exceptional spy family, so an ordinary friendship now carries security concerns far beyond the schoolyard.
Gigguku
Taiyo has one person he can truly talk to, and that person comes with the loudest possible family complication. Mutsumi's household is steeped in espionage, while her overprotective brother treats Taiyo like an active threat. His quiet loyalty crashes into spectacular family suspicion, and the contrast gives the comedy real heart!
Father's Basement
The espionage premise has very little interest in restraint, and the overprotective brother arrives at maximum intensity. Taiyo keeps it from becoming empty noise. He is isolated, sincere, and unwilling to abandon Mutsumi simply because her family is alarming. That modest loyalty gives the exaggerated conflict a clear emotional reason.