Yan Yan didn't know why he kept being reborn, met all kinds of people, and experienced goodwill and malice in society. However, after passing through mountains and rivers and seeing the vastness of the universe, he felt that human beings were really small and fragile, nothing more than a speck of dust under the vast sky.
Yan Yan has been living in other people's bodies, helping the host fulfill his/her wishes.
The heroine is something like a portable grandma [cross out], right?