Warning: The entire story is in first person, with other perspectives mixed in, so the point of view can be confusing.
Ye Xing was just living an ordinary life. Nothing special happened to her, but somehow she transmigrated all the same, and into the highly dangerous world of Katekyo Hitman Reborn, no less! What's more, she doesn't even know whether this is a world with the Future Arc. If it isn't, well, she's as good as dead.
Rather than wait around for someone to possibly save her in the future, she'd better save herself. So she trains like crazy. Surely that makes her seem like a positive, motivated person, right? But it seems a lot of people don't see it that way.
After Tsuna, Gokudera, Yamamoto, Hibari, Reborn, and others made a string of strange declarations, she finally realized what her problem was. Apparently, she really does have a problem?
The people driven to exhaustion by a certain someone: “Get some self-awareness, you idiot!”
This is a different world, where friends influence each other. So what will they be like? Perhaps they'll become braver, for the sake of a better future.
Theme: Make the world within your reach a better place.