"Brother, when you're not seeing us...what are you doing?" Lingling wondered and visited his brother's house with Sakuya, Yotsuba, Kaho, and Arya. However, he was absent, and unfortunately, the answer is pending. Yotsuba, who came to Lingling's house that night, declares that her brother is more likely to go out alone on Sunday! The two decide to follow the "Oppa Detectives"...