Because MC is reincarnated, born as a baby, grow up as 5-6 years old and is acting on her age as a kid. It's normal because not all kids acted like a mature adult. At least it's a bit realistic instead of a child becoming a prodigy at the age of 4-5 years old with people going crazy for her and being overly doting. If you don't like a reincarnated child acting on their own age, go read manhwa ╮(￣▽￣)╭
Yeah but consider the following
She has retained all her memories. WHY IS SHE CRUSHING ON A SIX YEAR OLD?
She's a child of course she's going to have a crush on a kid. Just because she have her previous life memories doesn't mean she's an adult already. She have a body of a child and a mind of child not a freaking adult. You guys are so weird for thinking that.
???? How does one retain 20+ years of memories and experience and just automatically regress to 6 year old mentality. It litteraly doesn't make sense. If she got vague memories and had insticts or sum yeah you'd have a case. All I see right now is that she is going to be visited by Chris Hansen soon.
They're the same age wtf. Do you want it to be like those manhwas or other mangas that married their guardians/love interests with a terrible age gap? At least the author set their age right instead making MC an adult. You're a creep for thinking like this.
So how old was she when she first died? Like I honestly don't get why they show us these stories from when they're six. Lady looked early twenties and she just acts super childish. Like bro she has all her memories but she doesn't grasp the seriousness of her situation at times. I only read the first 2 chapters but she's so...weird... crushing on a six year old. Ew. I seriously need to understand why no one commented about this.