In crossover anime, who isn't a childhood friend?

Starting in kindergarten, I got to know Yukinoshita, Hayasaka Ai, the Takanashi sisters...
[Male protagonist, multiple female leads, slice-of-life story]
Good news! Although I was killed by a dump truck, I managed to travel through time.
Bad news: I've been transmigrated into the body of a five-year-old toddler.
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My name is Yuan Qianye, and I am currently in the senior class of kindergarten.
Even though my body has shrunk, I'm not panicking at all.
Because my system has a "God's-eye view".
Under certain conditions, it is possible to observe others without regard to the laws of physics.
In addition, I can also bind with other people.
I will also get a share of the improved skills they gain through hard work.
Knowing this, the next step is quite simple...
(This story blends the worldviews of several popular slice-of-life anime series, and provides detailed descriptions of each main character. Even those unfamiliar with the original works can enjoy it as an original story.)