She's Pure
After transmigrating, she discovered that she had been born into the Haneda family as a posthumous child. From the moment she was born, she bore the heavy responsibility of avenging her father. To hide from the Organization, her mother left her in the care of her late father's sworn younger brother.
Akai Some: It's fine. I can handle it.
Young Sera: Are you my niece?
Akai Some: You're the straight one! Your whole family is straight!
As the younger generation, surely it's only natural to get away with all sorts of mischief by virtue of your junior status! Like whispering into Conan's ear the first time she saw him after he had shrunk: "Hello, Kudo Shinichi."
Or sweetly telling Subaru Okiya, "You look just like one of my uncles. His name is Akai Shuichi!"
Or telling Toru Amuro, "I'm a new member of the Organization. My codename is Erguotou."
Or, when she saw Ai Haibara, calling out, "Auntie..."
Huh? Something seems off...
Causing trouble and taking it easy in the world of the Grim Reaper Elementary School Detective, teasing the main characters along the way, Akai Some declares that she absolutely won't let any of you take advantage of her!
Haibara: Call me Auntie.
Akai Some: ...
This is a slow-burn story that follows the main plot, with Ai Haibara as the pairing, one-on-one.