Koisuru Otome to Shugo no Tate: The Code Name is "SHIELD-9"

Koisuru Otome to Shugo no Tate: The Code Name is "SHIELD-9" is a Japanese adult visual novel about a crossdressing bodyguard who is assigned to infiltrate an all-girls' school in order to protect two students.

Shuuji Kisaragi (codename: SHIELD-9) is a young bodyguard who works for a personal security organization called Aigis Security. Shuuji has grown into his role at Aigis, having been adopted by the chief of the VIP protection division after the deaths of his parents. Shuuji's current assignment is to go undercover as a schoolgirl named Taeko Yamada in order to infiltrate an all-girls' school, St. Theresa Gakuen, to protect two students from unknown attackers. These students are Yukino Kasugazaki, the wealthy president of the student council, and Ren Tsubakihara, the tomboyish vice president. As Shuuji spends his days with these girls and more, he begins to develop feelings for them.

The player makes decisions throughout the game which may cause the story to branch into different routes and result in different endings. The game features five heroines including Yukino and Ren, all students. The others are the energetic Yuuri Homura, the reserved Setsuko Sanada, and the mischievous Marina Shinjou.

The Windows version includes scenes with sexual content which were omitted from the mobile versions.