Although Aoto and Chiba Sonako are not particularly close, and he hasn't spoken with her much, she is, after all, the sister of Chiba Shigetarou and the cousin of Chiba Eijiro.
Chiba Shigetarou is a good friend of Aoto, and Chiba Eijiro recently gave him some selfless guidance in Martial Arts... Just for these reasons alone, Aoto is determined to go all out in search of the missing Chiba Sonako.
Aoto has a rough plan on how to investigate Nakamura Chouhachirou.
He highly suspects that Nakamura Tsuki and Chiba Sonako were kidnapped by someone for certain reasons.
The kidnappers demanded that Nakamura Chouhachirou must conceal the fact of Nakamura Tsuki's abduction, or else they would kill, which is why Nakamura Chouhachirou spouted nonsense about "Nakamura Tsuki going to Osaka to see her grandmother."
